As long as server was created using hostname, then the underlying IP address change should not have any effects. Validate this by going into QMC > Nodes and parsing the Host name column. Is here is the IP and not the IP it will be a different procedure on the qlik side.
Also, keep in mind that the databases you connect to from Qlik (such as SQL or PostgreSQL) may have the Qlik server's IP address on their whitelist.
Last, if for any reason a user accesses the server by IP address and not by hostname, you will need to add the new IP address in the Virtual Proxy settings -> advanced -> Host allow list
i would suggest a full server reboot after the change
