After bashing my head against the wall for a little while, I finally had the bright idea of trying to encrypt a message from the command line:
Send operation aborted. Key 0xABCDEF01 not found or not valid. The (sub-)key might have expired.
baitisj@foo:/tmp$ gpg -e -r firstname.lastname@example.org -a -s
gpg-agent: can't connect to the PIN entry module: IPC connect call failed
gpg-agent: command get_passphrase failed: No pinentry
baitisj@foo:/tmp$ sudo pkg install pinentry-gtk2