Premature License Expiration

From the licensing portal, I deleted my existing license, created a new one, uploaded and applied the new license, rebooted the UTM, and am now able to login again.

It's back again. Appears to reoccur after a reboot:

As said earlier: check the clock.

ssh into it (should still be possible) and try "hwclock".

Maybe the battery for the clock (usually a CR2032 button cell) died, the box comes up with a faulty date (earlier than 03/11/2023) and later learns the correct time via NTP.
"dmesg" or "cat /var/log/messages" should show the entire boot process with timestamps.

As said earlier: check the clock.

ssh into it (should still be possible) and try "hwclock".

Maybe the battery for the clock (usually a CR2032 button cell) died, the box comes up with a faulty date (earlier than 03/11/2023) and later learns the correct time via NTP.
"dmesg" or "cat /var/log/messages" should show the entire boot process with timestamps.