Think project-gc is still handling the issues with the new geocaching.com API.
As there are these authenticators issues also on the GC.com site (as you mentioned), project-gc perhaps wait until gc.com has fixed there issues.
Have the same problem using project-gc and also have the same issues with firefox, chrome on my deviced getting into gc.com
We all like single sugn on and authenticators only once - but we all like security (with our username, pw and account). Think they are just try to get this as useful as possible.
==> think we have to wait