Symptoms
The error "The K2 URL is not Valid" appears when attempting to register the K2 url in the K2 blackpearl for SharePoint app's Registration Wizard.
Diagnoses
On the K2 host server logs, the following error is found at the time of the K2 URL validation on the K2 App Registration Wizard:
Error 2025 Error Marshalling SourceCode.EnvironmentSettings.Runtime.EnvironmentSettingsHostableServer.GetAutoDiscoverServerInfo, Primary Credentials Not Authenticated
Accessing the K2 AutoDiscover URL also produces the same error.
K2 AutoDiscover URL: http://[k2 url]/AutoDiscover/AutoDiscover
Resolution
ASP.NET Impersonation was turned on under the Authentication settings for the K2 AutoDiscover site in IIS. After turning it off and performing an IISRESET, the AutoDiscover works as expected, and the error "The K2 URL is not Valid" no longer appears.
