This is indeed a strange issue, however it seems to have something to do with licensing. Do a show version and check to see if you are running a valid license key.
Another possible reason is that you have configured the interface as part of a bridge group. If that is the case, remove the
bridge-group command to be able to assign an IP address.
A third reason for not being able to set up an IP address on an interface is if you are in multiple context mode. This is where you can partition an ASA into multiple logical devices. Make sure you are in single context mode. To do so, take a look at this Cisco documentation:
I hope that this helps getting you started in your troubleshooting…
I hope this has been helpful!