We’ve long been recommending the use of CrmServiceClient in your applications that connect to Dynamics 365. But what to do when the client just wouldn’t connect?
The easiest way to start troubleshooting connectivity to Dynamics 365 is to run LoginControlTester.exe that has long been part of the SDK and can be found in <SDK>\Bin folder. As the name suggest, when you run it, the standard Xrm Tooling login dialog is displayed and it gives you a short Aye or Nay. The difference is that in config file for this small app tracing levels are maxed out and, in addition, there are some listeners for IdentityModel, ServiceModel, and even ADAL.
After you run the tests, collect your output in the same folder in the form of LoginControlTesterLog.txt and CrmToolBox.svclog files. You can use notepad of your choice to mule over the .txt file content, .svclog file can be viewed by Service Trace Viewer that is part of .NET tooling. Chances are that you’ll be able just double-click .svclog file to get it open.
Lots of troubleshooting goodness here, and if you’re dealing with the support to resolve the issue, these files are something they would definitely ask for (or they should).