我正在尝试通过JavaPayPalSDK连接到我的paypal业务帐户，以自动发送发票。我将.properties文件配置为：

http.ConnectionTimeOut=5000
http.Retry=1
http.ReadTimeOut=30000
http.MaxConnection=100
# HTTP Proxy configuration
# If you are using proxy set http.UseProxy to true and replace the following
values with your proxy parameters
http.ProxyPort=8080
http.ProxyHost=127.0.0.1
http.UseProxy=false
http.ProxyUserName=null
http.ProxyPassword=null
# Set this property to true if you are using the PayPal SDK within a Google
App Engine java app
http.GoogleAppEngine = false
# Service Configuration
service.EndPoint=https://api.sandbox.paypal.com
# Live EndPoint
# service.EndPoint=https://api.paypal.com
# Credentials
clientId=ID (of SANDBOX API CREDENTIALS)
clientSecret=SECRET (of SANDBOX API CREDENTIALS)
# Webhook Validation
# webhook.trustCert=DigiCertSHA2ExtendedValidationServerCA.crt

当它连接时，我得到“错误消息：应用程序属性中没有配置api帐户”。我的.properties文件有什么问题？