The get_unlock_ability returning 0 seems strange as you had recently unlocked it correct so it would have had to be allowed? There has been some confusion in the past months with some Fairphone users that effectively ended up with bricked devices because of what I thought was related to first reinstalling FPOS (and not locking (??) at the end but it may possibly have set get_unlock_ability to 0 even though the device remained unlocked?), then ending up like you: they relocked at the end of the iodéOS install and couldn’t unlock again.
The iodéOS install does not change get_unlock_ability to 0, so if it reports that it must have been like that before iodéOS install, but then I still can’t sort out what led to what in that case.
I think an important note for our installation process may be to make sure that users manually confirm Allow OEM Unlocking is enabled from Developer Options before they install, just to make sure.
There is a FP6 post in the past day as well that may be in a similar situation. In addition, upgrades to v7.2 beta for a FP6 user with a locked bootloader left it unbootable, it then reverted to the prior v7.1 install so that beta was discarded. This last one matches issues we have seen for FP4 users upgrading to v7.x: if the bootloader is locked then it refuses to boot. This also is not solved.
So there are getting to be a growing number of issues with FP + locked bootloaders. Some on new installs, some after upgrading. I will pass a reference to this post the developers.