It happens that the friending is not properly configured, or simply failing, with a specific remote application. To get more information about it, we can try to set up a Project Association with this remote application.
During the Project Association procedure, after selecting the Association Type, you will either see an error notification in a popup window (similar to the below first example), or an error from your OSLC application itself.
Possible causes can be:
in ELM, when the consumer key was deleted from the OSLC Connect application
in Polarion, when the consumer key has been deleted in the OSLC Connect application
in ELM, when the consumer key exists, but the consumer secret is invalid
in Polarion, when the consumer key exists, but the consumer secret is invalid