PGP keys can expire and be renewed.
If you've checked that the PGP fingerprint is correct and yet your PGP/GPG application still says our key is expired, you most likely downloaded our public key prior to it being renewed.
Timeline of our public key for firstname.lastname@example.org:
- Created on October 16, 2012
- Expired on October 15, 2017
- Renewed until October 14, 2019