The region change option is not available for the accounts registered in European Economic Area (EEA) due to General Data Protection Regulation (GDPR), @Unknown user.
This is most probably due to your internet connection, @Unknown user. Please try to do a Routine Repair of the game, clear game cache and reset network settings one time. You can reset your network settings through device settings > System > Reset Options > Reset WiFi, mobile & Bluetooth. Restart your device.