I have 16 of the IP2m-841 IP cameras. I had one that continually gave me a "Nu;; is not allowed" when trying to set the ip to a static configuration. Even resetting did not resolve my issue.
In my case, the issues was in Settings> Network>TCP area. On IP Version: select IPv6 (which I never use). At the bottom, I Reset Defaults and saved.
When I went back to the IPv4 to set the static IP, it worked. Hope this helps someone else with this frustration. Thanks Ron
Null is not Allowed issue - solved with IP Version reset
Re: Null is not Allowed issue - solved with IP Version reset
I was having the same problem with my IP4M-1041W. Your solution worked perfectly. Thank you very much!!!! You saved me lots of time.