Flashed the firmware but specifically ensured the userdata partition was rewritten to clear the lock.

/dev/block/mmcblk0p48 /data ext4 rw,seclabel,nosuid,nodev,noatime,noauto_da_alloc,resuid=1000,resgid=1000,errors=panic,data=ordered 0 0

If your phone warns of "Insufficient Storage," you need to clear unnecessary userdata:

Select to create a backup file on the internal storage.