Hi there, kindly check the earphone is connected properly and share the screenshot of the notification bar if the earphone sign appears so that we can understand the issue better.
You may also follow the below steps:
1. Clear system cache.
2. Try the same under safe mode:
Hold the power button for 5 seconds => When the screen flashes with option => Press & hold power option => You will get an option to restart in safe mode
3. If still you face the issue
factory reset your phone after taking a full backup :
https://www.asus.com/support/FAQ/1006346/