Causes:
There are two possible reasons for the error message “IP address has changed” from cPanel/webmail.
1) Your Internet Service Provider (ISP) has a short DHCP lease time, causing your IP address to be renewed/released and reassigned while you are logged into cPanel/Webmail.
2) You are attempting to log in to cPanel using the same account from two different devices concurrently.
Suggested Fix:
Retry login with the following links instead:
1. For Cpanel, use serverIP/cpanel or ServerIP:2083. For example https://123.456.7.8/cpanel or https://123.456.7.8:2083
2) For Webmail, use serverIP/webmail or ServerIP:2095. For example https://123.456.7.8/webmail or https://123.456.7.8:2095
Other possible causes of the error are:
1. The date on your computer is set incorrectly or in the future causing the session to expire
2. Having a software/plugin/setting that blocks third-party cookies aggressively (things like anti-virus software)
3. Your browser is not set to accept cookies (browser settings)
4. You have some sort of proxy service/ firewall configured (service like Succuri/ Cloudflare services might need to be bypassed.)
5. Your IP is dynamically changing (typically office network set up/ host IP leases to modem/router)
6. You are using Cloudflare - in this case, you need to exclude the address for your webmail/Cpanel from CF so that CF is bypassed. If you have VPS/Cloud server you can disable the IP Cookie validation