Bad idea to use a different IP address. In fact, if you use the same IP address as your previous avast server, your clients will pull updates from it without a problem. You can then do a network discover in the avast console and avast will automaticall re-detect all your endpoints.

If you DID change the server IP, then you’ll have to go to the console and reinstall avast on all the computers in bulk. You don’t have to go workstation to workstation if you’re lucky. I had this problem a while back, new server, new IP, and the re-install from console did not work and neither did removal. I had to uninstall avast manually on 200 workstations!!! bulk uninstall is very difficult because of the program protection, but bulk install is easy.