The error message “Your IP address has changed. Please log in again” seems to be most common among Telkom customers. Most notably, their LTE customers have been receiving this error due to a change they made on their end.
Please follow this device setup guide ensuring that the Profile name and APN are set to "unrestricted".
If you are uncertain about making the change, please contact Telkom on 081 180 or 10210/10213 or contact your LTE service provider.