下面的代码可以工作，但是你不应该使用p元素来点击。使用a或button会更好。

import React, {useState} from 'react'

const signupStates = {
  login: "login",
  signup: "signup",
  adminLogin: "adminLogin"
}

const LoginPage = () => {
  const [signupState, setSignupState] = useState(signupStates.login);

  const LoginForm = () => {
    return (
      <div className="bg-white rounded-2xl shadow-2xl flex flex-col w-full md:w-1/3 items-center max-w-4xl transition duration-1000 ease-out">
        <h2 className='p-3 text-3xl font-bold text-pink-400'>Jupiter Review Hub</h2>
        <div className="inline-block border-[1px] justify-center w-20 border-blue-400 border-solid"></div>
        <h3 className='text-xl font-semibold text-blue-400 pt-2'>Log in</h3>

        {/* Inputs */}
        <div className='flex flex-col items-center justify-center'>
          <input type='email' className='rounded-2xl px-2 py-1 w-4/5  text-blue-500 md:w-full border-[1px] border-blue-400 m-1 focus:shadow-md focus:border-pink-400 focus:outline-none focus:ring-0' placeholder='Email'></input>
          <input type="password" className='rounded-2xl px-2 py-1 w-4/5  text-blue-500 md:w-full border-[1px] border-blue-400 m-1 focus:shadow-md focus:border-pink-400 focus:outline-none focus:ring-0' placeholder='Password'></input>
          <button className='rounded-2xl m-2 text-white bg-blue-400 w-2/5 px-4 py-2 shadow-md hover:text-blue-400 hover:bg-white transition duration-200 ease-in'>
            Log in
          </button>
        </div>
        <div className="inline-block border-[1px] justify-center w-20 border-blue-400 border-solid"></div>
        <p className='text-blue-400 mt-4 text-sm'>Don't have an account?</p>
        <p className='text-blue-400 mb-4 text-sm font-medium cursor-pointer' onClick={() => setSignupState(signupStates.signup)}>Register here</p>
        <p className='text-blue-400 mt-4 text-sm'>OR</p>
        <p className='text-blue-400 mb-4 text-sm font-medium cursor-pointer' onClick={() => setSignupState(signupStates.adminLogin)}>Login as an Admin</p>

      </div>
    )
  }

  const SignUpForm = () => {
    return (
      <div className="bg-blue-400 text-white rounded-2xl shadow-2xl  flex flex-col w-full  md:w-1/3 items-center max-w-4xl transition duration-1000 ease-in">
        <h2 className='p-3 text-3xl font-bold text-white'>Jupiter Review Hub</h2>
        <div className="inline-block border-[1px] justify-center w-20 border-white border-solid"></div>
        <h3 className='text-xl font-semibold text-white pt-2'>Create account</h3>

        {/* Inputs */}
        <div className='flex flex-col items-center justify-center mt-2'>
          <input type="text" className='rounded-2xl px-2 py-1 w-4/5   text-blue-500 md:w-full border-[1px] border-blue-400 m-1 focus:shadow-md focus:border-pink-400 focus:outline-none focus:ring-0' placeholder='Name'></input>
          <input type='email' className='rounded-2xl px-2 py-1 w-4/5  text-blue-500 md:w-full border-[1px] border-blue-400 m-1 focus:shadow-md focus:border-pink-400 focus:outline-none focus:ring-0' placeholder='Email'></input>
          <input type="password" className='rounded-2xl px-2 py-1 w-4/5  text-blue-500 md:w-full border-[1px] border-blue-400 m-1 focus:shadow-md focus:border-pink-400 focus:outline-none focus:ring-0' placeholder='Password'></input>
          <button className='rounded-2xl m-4 text-blue-400 bg-white w-3/5 px-4 py-2 shadow-md hover:text-white hover:bg-blue-400 transition duration-200 ease-in'>
            Register
          </button>
        </div>
        <div className="inline-block border-[1px] justify-center w-20 border-white border-solid"></div>
        <p className='text-white mt-4 text-sm'>Already have an account?</p>
        <p className='text-white mb-4 text-sm font-medium cursor-pointer' onClick={() => setSignupState(signupStates.login)}>Click here to Log in</p>
      </div>
    )
  }
  const AdminLoginForm = () => {
    return (
      <div className="bg-white rounded-2xl shadow-2xl flex flex-col w-full md:w-1/3 items-center max-w-4xl transition duration-1000 ease-out">
        <h2 className='p-3 text-3xl font-bold text-pink-400'>Jupiter Review Hub</h2>
        <div className="inline-block border-[1px] justify-center w-20 border-blue-400 border-solid"></div>
        <h3 className='text-xl font-semibold text-blue-400 pt-2'>Admin Log in</h3>

        {/* Inputs */}
        <div className='flex flex-col items-center justify-center'>
          <input type='email' className='rounded-2xl px-2 py-1 w-4/5  text-blue-500 md:w-full border-[1px] border-blue-400 m-1 focus:shadow-md focus:border-pink-400 focus:outline-none focus:ring-0' placeholder='Email'></input>
          <input type="password" className='rounded-2xl px-2 py-1 w-4/5  text-blue-500 md:w-full border-[1px] border-blue-400 m-1 focus:shadow-md focus:border-pink-400 focus:outline-none focus:ring-0' placeholder='Password'></input>
          <button className='rounded-2xl m-2 text-white bg-blue-400 w-2/5 px-4 py-2 shadow-md hover:text-blue-400 hover:bg-white transition duration-200 ease-in'>
            Log in
          </button>
        </div>
        <div className="inline-block border-[1px] justify-center w-20 border-blue-400 border-solid"></div>
        <p className='text-blue-400 mt-4 text-sm'>Don't have an account?</p>
        <p className='text-blue-400 mb-4 text-sm font-medium cursor-pointer' onClick={() => setSignupState(signupStates.signup)}>Register here</p>
      </div>
    )
  }
  
  const UserAuth = () => {
    if (signupState === signupStates.login) {
      return <LoginForm />
    }
    
    if (signupState === signupStates.signup) {
      return <SignUpForm />
    }
    
    if (signupState === signupStates.adminLogin) {
      return <AdminLoginForm />
    }

    return null;
  }

  return (
    <div className="bg-gray-100 flex flex-col items-center justify-center min-h-screen md:py-2">
      <main className="flex items-center w-full px-2 md:px-20">
        <div className="hidden md:inline-flex flex-col flex-1 space-y-1">
          <p className='text-6xl text-blue-500 font-bold'>Jupiter Review Hub</p>
          <p className='font-medium text-lg leading-1 text-pink-400'>Your voice matters - Rate your Jupiter hostel stay with | Jupiter Review Hub |</p>
        </div>

        <UserAuth />
        
      </main>
    </div>
  )
}

export default LoginPage

我认为你需要在Login as an admin的onClick事件中将setIsLogin设置为true。
使用下面的代码尝试一次：

const LoginForm = () => {
  return (
    <div className="bg-white rounded-2xl shadow-2xl flex flex-col w-full md:w-1/3 items-center max-w-4xl transition duration-1000 ease-out">
      <h2 className="p-3 text-3xl font-bold text-pink-400">
        Jupiter Review Hub
      </h2>
      <div className="inline-block border-[1px] justify-center w-20 border-blue-400 border-solid"></div>
      <h3 className="text-xl font-semibold text-blue-400 pt-2">Log in</h3>

      {/* Inputs */}
      <div className="flex flex-col items-center justify-center">
        <input
          type="email"
          className="rounded-2xl px-2 py-1 w-4/5  text-blue-500 md:w-full border-[1px] border-blue-400 m-1 focus:shadow-md focus:border-pink-400 focus:outline-none focus:ring-0"
          placeholder="Email"
        ></input>
        <input
          type="password"
          className="rounded-2xl px-2 py-1 w-4/5  text-blue-500 md:w-full border-[1px] border-blue-400 m-1 focus:shadow-md focus:border-pink-400 focus:outline-none focus:ring-0"
          placeholder="Password"
        ></input>
        <button className="rounded-2xl m-2 text-white bg-blue-400 w-2/5 px-4 py-2 shadow-md hover:text-blue-400 hover:bg-white transition duration-200 ease-in">
          Log in
        </button>
      </div>
      <div className="inline-block border-[1px] justify-center w-20 border-blue-400 border-solid"></div>
      <p className="text-blue-400 mt-4 text-sm">Don't have an account?</p>
      <p
        className="text-blue-400 mb-4 text-sm font-medium cursor-pointer"
        onClick={() => setIsLogin(false) && setIsSignUp(true)}
      >
        Register here
      </p>
      <p className="text-blue-400 mt-4 text-sm">OR</p>
      <p
        className="text-blue-400 mb-4 text-sm font-medium cursor-pointer"
        onClick={() => {
          setIsLogin(true);  //Change this to true
          setIsAdmin(true);
          setIsSignUp(false);
         }
        }
      >
        Login as an Admin
      </p>
    </div>
  );
};