Hi @notacat welcome to the /e/ forum.
You could first try Issues with the Updater and a solution – be sure to correctly reboot the phone after (even by removal of battery if unsure).
You should backup essentials before any intervention.
To bring the phone up to date will involve Android version upgrade to Android 13 (T).
Here is a link to the OTA file https://ota.ecloud.global/official/FP3/e-2.5-t-20241111446629-official-FP3.zip.
Here is a link to the method recently described for FP4 2 identical FP4's one is stuck at e os 1.21.1 - #6 by piero
- stable builds have been redesignated official since your current build Different Build Types