I changed the server IP address and after it, I can't see the admin panel. Any configuration file must be edit?
Please check app/etc/env.php file, what host you have added in this. If it exists old IP address just replace it with new IP and clear Magento cache.
Or if you running website with IP address only then change it into core_config_data table also in database.
If both not work please share exact issue with admin panel so that can help to understand issue. Thanks
go to Admin>>System>>Configuration>>Advanced>>Admin.
Click on Admin Base Url.
Click drop down in front of Use Custom Admin Url to "Yes" and Add your custom admin Url.
If you want to add the Custom Admin path you can manage by enabling the Use Custom Admin path.