Server/Client install on LAN, suddern change in connection problems

I am running a long established backup install for 6 local computers. The setup has served me pretty well for years now with not many problems and fairly easily solvable. This one has me stumped though.
I am running Server vers 2.2.11 and clients vers 2,2,6 .OK you are all going to say update, but this has worked for me and I saw no need to.The system worked up until today. It backed up 1 computer yesterday and 1 the day before. Today it will not do any.
I have rebooted everything and checked connections such as firewalls and apps allowed through the firewalls. One computer being backed up is the same one the server is installed. So the firewall for that client shouldn’t matter.
The server shows clients as online, but I cannot manually start a backup. 3 of the clients at least show the status as idle, but the toolbar icon is red which i guess means a fault.
I have tried everything I can think of. Anyone have any suggestions please???

OOOPS!! Shortly after having posted the above I noticed something - and then gradually realised my mistake!
The computer I use as my server does duty as all manner of backups and data archiving on a total of 8 individual drives. For some reason i have yet to explain, 4 of them were not showing up in the system (Win10 Pro). So, I did what I generally do, shut down, reconnected plugs and wiggle cables - and they all now show up. And Urbackup is now running a couple of backups, since it now has access to its backup drive. Sigh, I am an older analogue techie, sometimes I hate technology!