Go to the admin web page of your Nucleus and check if it is up to date. Open your internet browser and try http://nucleus or if this does not work try http://nucleus.local. If this does not work either, use the IP address of the Nucleus instead of “nucleus”
The Roon Server version should be build 1223 production. If it is lower you may be a victim of this recent quite frequent issue:
It seems that current releases of control devices / remotes crash when the Core is not up do date. Some Cores, however, seem to have got stuck at an older build and then this happens. If all your remotes crash then you can’t initiate the update from the remote but you can trigger the update by going to the admin web page and clicking the Reinstall button for the Operating System:
If you clicked the Reinstall button for “Operating System” as recommended, then I don’t know why that didn’t trigger the update for the Roon Server, because this did help in many other cases. If this remains the case, paging @support who can trigger the update remotely for you
Is there some reason why you are using a static IP address rather than using DHCP? I just wonder if that might have something to do with the fact that reinstalling Roon OS has not worked for you? It seems to be working for others who have reported this issue.
Unfortunately, there are lots of incorrect myths out there about static being somehow better. Usually from 30 years ago because someone once had a bug in an DHCP implementation.
Nowadays, DHCP is nearly always better except on maybe some very rare and special circumstances. Static addresses require a lot of care whenever something changes in the network, not recommended