Ok, with OEM unlocking enabled this is officially odd.
Safe route: Contact support (forum consensus is to call them for a chance to get results quickly) … https://support.fairphone.com/hc/en-us
Adventurous route: Fairphone 3 unlocking without oem unlocking
(if this still works, last mention of it working I found was end of August 2022)
I would recommend the safe route first.