When we struggled with this error in cPanel while logging in
Your IP address has changed. Please log in again.
The root cause of this hurdle. Your Internet Service Provider (ISP) has a negligible DHCP lease time, causing IP address to be renewed/released and reassigned while you are logged into cPanel. Another way to say it, you don't have a static IP address.
How you would check your internet IP static or not?
Open IP checker site --> https://www.whatismyip.com/ - Refresh the page and keep an eye on IPV4. if the My Public IPV4 changed on each page refresh then it isn't static.
ISP (Internet Service Provider) can have to get charged extra to provide a STATIC IP or they will enforce you to upgrade pkg.