Same with me. I have two Teracubes 2e (bought in May '23), one of which could not be updated for a year now (Android 11, iodéOS 2.11). I contacted Antoine for help from iodé but received none. In July I posted a request to the community - no reply either (Teracube 2e - update 2.12 coninuously failes). I was thinking I was the only one with this sort of problem … Tried updating several times, nothing worked, even reset to factory settings failed solving the issue.
Try the following: open “iode news” on your phone, choose “join/participate” (or whatever the Englisch word for “Mitmachen”), then “Become a beta tester” and follow the link (github). Donwload the installer (it replaces the one on your phone). I tried this for one of the two Teracubes and it worked. The phone even got promoted to Android 12 (very nice), iodé is now 3.10. There is a downside, though: Being a beta tester means that some updates may not work properly - one crashed my phone entirely and I lost everything.
But then … since there are now two of us, maybe we get heard in the community! In any case, keep me informed.