I recently ran into the same problem but not related to upgrading the server. We were not able to see build process templates when trying to add a new build definition. We are in TFS 2012. This team project also appeared not to have any build definitions. That was expected though because we had not yet used the TFS builds on this team project.
The problem was caused by someone with admin rights setting the "View build definition" and the "View Builds" access rights to Deny for everyone.
By just setting that back to allow on the TFS group, we suddenly could see the build definitions and also were able to select build process templates.
It was really strange that it let us add new build process templates, but we couldn't select them.