When you have a solution that is created from a Sharepoint list and you choose to create a workflow which should start once a list item is added, it fails to work. The workflow still works if started manually.
This happens with legacy workflows that were created on 4.6.11 and earlier versions.
You will notice an error within the hostserver log file which can be seen within the following location:
Program Files x 86 > K2 Blackpearl > Host Server > Bin, outlining the following:
"Error","IdentityService","64018","SharePointGroupProviderResolveNameException", "SPCsomClient.GetUser","64018 Failed to resolve user 'i:0i.t|00000003-0000-0ff1-ce00-000000000000|app@sharepoint' on SharePoint site 'https://###.sharepoint.com/sites/***',
Error: System.Reflection.TargetInvocationException: An unexpected failure was encountered when contacting SharePoint to get information from the group provider CSR: Key cannot be null. Parameter name: key ---> System.ArgumentNullException: Key cannot be null"
To resolve this issue please follow the instructions within the KB article below which would require a direct modification within the hostserver.exe.config file. This should be in the same location as the host server log file as mentioned above:
The workflow should start automatically again as expected.