If logged in into a SSH server with a running desktop, the GPG tool doesn’t show any password dialog when trying to decrypt a file in an SSH session. It just stalls at gpg: AES encrypted data.
User grawity shows a solution on superuser.com where the PIN-Entry tool of the GPG agent can be set manually. My adaption now looks like this and works like a charm:
Reload the GPG agent configuration with the following command and you’re done:
gpg-connect-agent reloadagent /bye