Note:  This is an old article.  However, the troubleshooting tips may still apply to newer versions. 

Symptoms

You receive the following error when connecting to CRM online using the CRM adapter:

Value cannot be null. Parameter name: authenticationCredentials.SupportingCredentials

Solution

Replace the local discovery service URL (ie company.crm.dynamics.com) with the generic CRM discovery service. The following is the list of CRM discovery server URLs.