Hi,

Currently my organization have a web service that would periodically update information into salesforce. Until recently we are unable to gain access to Salesforce. Our logs only shows the error message below. 

 --> The remote server returned an error: (500) Internal Server Error. 
System.Net.WebException: The remote server returned an error: (500) Internal Server Error. 
   at OrderWF.SF.SyncWindowsService.SyncAdvCustToSF.CallSFService(String accessToken) 
   at OrderWF.SF.SyncWindowsService.SyncAdvCustToSF.ProcessSync() 

And below are the information from the web config files that we would update the password and security token every 60days.
I have double check the password and security token information to be correct. 

    <add key="SFAdvCustNoOAuthService.ServiceURL" value="https://login.salesforce.com/services/oauth2/token"/>
    <add key="SFAdvCustNoOAuthService.GrantType" value="password"/>
    <add key="SFAdvCustNoOAuthService.ClientId" value="3MVG9WtWSKUDG.x6rq8gfzguj0ran8aXqFOEpmn7PiIHr2fCNw35hAarblEiDbT4gO8Wn7dBWTNGqN2uyKQSP"/>
    <add key="SFAdvCustNoOAuthService.ClientSecret" value="4729694440366245264"/>
    <add key="SFAdvCustNoOAuthService.Username" value="(Hide)"/>
    <add key="SFAdvCustNoOAuthService.Password" value="(Hide)"/>
    <add key="SFAdvCustNoOAuthService.SecurityToken" value="(Hide)"/>
    <add key="SFAdvCustNoService.ServiceURL" value="https://emea.salesforce.com/services/apexrest/AdvCustNoService"/>
    <add key="Timer.Interval" value="300000"/><!--1 min = 60000 miliseconds-->

Would appreciate any suggestion or help to resolve the issue.

Thanks

Regards