Renew an expired key

renew edit-key expire trust

Source

https://gist.github.com/krisleech/760213ed287ea9da85521c7c9aac1df0

gpg --edit-key KEYID

In the GPG prompt:

gpg> expire

Now choose a new expiry date (e.g. 2y for 2 years)

Optionally, do this for all subkeys (the primary key is 0):

gpg> key 1
gpg> key 2
...
gpg> expire

Since the key has changed it needs to be trusted again:

gpg> trust

Finally, save the changes:

gpg> save

Then, export the key again and publish it to a key server.