Having CREATE TABLE permissions at the database level doesn't grant the user the ability to actually create a table. In addition they must have permissions on the target schema.

The correct grants for a user to be able to create tables in a schema is to grant the user or a role they are in ownership of the schema, eg

create schema foo
go
create role foo_owners 
go
alter authorization on schema::foo to foo_owners
go

grant create table to foo_owners;

create user a_foo_owner without login

alter role foo_owners add member a_foo_owner

go

You don't just grant privileges on a schema owned by another user, or they could create objects with intact ownership chains to other schemas owned by the schema owner.