OK so this seems to match the FP5 user with a similiar issue. I can’t understand how you had unlocked the devices before installing iodéOS if get_unlock_ability was 0? Any insights there would help for “post mortem” but unfortunately if it is truly unlockable and it doesn’t boot then it is not something we can solve… it may need warranty service?
Note that if a device fails to boot ??5-6?? times successively it should revert to the “other slot” (prior installation). Let’s hope that would happen, but possibly the install process wiped both A and B slots?