Steve on 23 Mar, 2020 10:11 PM
welcome to the GPGTools support platform. Sorry you are having problems using GPG Suite.
It seems your OpenPGP Key and or Subkey may have expired. This KB-article explains how to extend the expiry date of your Key and Subkey in case it will soon expire or has already expired.
Newer versions of GPG Suite now show a warning before your key expires and allow you to easily extend the key. If you can we would recommend to update your OS to a newer release as macOS 10.11 is no longer supported by recent GPG Suite versions.