After upgrading from 2.0.x to 2.2.x gpg started telling me that I have no subkeys to sign with, and my master key is not present on this machine. After trying various versions I finally figured out that going from the last 2.0.x to the first 2.1.x release upgrades to a new keybox format, and thinks that all of my subkeys have expired. If I run gpg -K -v, it shows them, but it shows the original expiration date for my currently active subkeys. I had extended the expiration date previously in 2.0.x and it had no problem with that, but 2.1+ seems to not see the extension.