Did you kept the rngd service up while upgrading ?
I tried the update on an instance that was a little bit older and still on candelpin 4.4.10 and got stuck the same way until I installed rng-tools and run the service as explained here: Status code: 403 for Error: Failed to download metadata for repo after upgrade to 3.11
Anyway, I can confirm that the workaround with rng-tools is fully working on 2 different instances with the same issue but not the same databases contents (they are not linked, one is my personal instance at home while the other is a production instance at work).
Best Regards,
Nicolas.