When clicking on the magnifying glass or the plus icon next to an entry in the message log you just get empty details:
Warden uses the systemd-journal to lookup mail log information. If your logs are empty you might have a corrupted journal. You can check with the command:
journalctl --verify
Journald log retention options are controlled in file /etc/systemd/journald.conf. Here is a KB article about them:
https://tecadmin.net/clear-systemd-journal-logs/
The SystemMaxUse and MaxRetentionSec options control the journal data retention limits.