Please let us to know this problem is resolved or not and if resolved then reply here with some more information.
I had the same problem not being able to install apps until I removed the version 3.6.36 completely and reinstalled the old version 3.3.86. I tried others in between but none worked. The expired certificate removal advice didn't work for me. I contacted Nokia Support, but they were unable to help, friendly, but no help sadly. They couldn't even provide the older version. I hope they fix that issue in a future version. The 3.7 beta version didn't work either by the way. I downloaded the old version here:
Hi, I am also facing the same issue with my c5-05. Every time I try to download any app, I get a msg 'Can't connect to service'