How can I fix this?
Please make sure you've selected 4G in mobile network settings. Please also check with your operator about the problem.
If the problem still appears, we suggest that you downgrade. You may find the downgrade method "Version ZC554K_P_downgrade_to_O" here: https://www.asus.com/Phone/ZenFone-4-Max-ZC554KL/HelpDesk_BIOS/
Thank you 🙂