Can't open the solution service

Jan 5 at 7:51 AM
Dear All
Once I am trying to open the PQM I am getting the following message:
"The active solution has been temporarily disconnected from source control because the server is unavailable. To attempt to reconnect to source control, close and then re-open the solution when the server is available. If you want to connect this solution to another server, use the Change Source Control dialog."

Can anyone please tell me how to solve this problem