Symptoms

On attempt to access the tab CCP > Office 365 the following error is displayed:

Unknown error occurred

The following error can be fount in browser debug console:

[HttpCompileException]: c:\inetpub\wwwroot\O365App\App_Code\ServiceProvider\PC\PcCustomerManager.cs(22): error CS0101: The namespace 'Parallels.Office365.Ga
teway.ServiceProvider.PC' already contains a definition for 'PcCustomerManager'
   at System.Web.Compilation.AssemblyBuilder.Compile()
   at System.Web.Compilation.BuildProvidersCompiler.PerformBuild()
...

Note: the file name can differ from PcCustomerManager.cs.

Cause

There is a duplicate or backup of the file PcCustomerManager.cs in the App_Code directory of the endpoint. IIS loads and process all available *.cs files in the application code directory and encounters the error ...already contains a definition for... in case some namespace is defined twice.

Resolution

Check the App_Code directory for a duplicate of the reported file and move it to a different location. It is also recommended to recycle IIS application pool after this.

Internal content