Proximity sensor serious issue

[AGalaxyuser]

My phone's proximity sensor sometimes won't work and sometimes works normally. Again same problem arises from the past 2 days.It won't work. Using a full screen protector that doesn't cover the sensor. How to fix the problem. 

[vishallote1989]

Which model you are using?

[AGalaxyuser]

M20

[vishallote1989]

Have you applied Edge to Edge Edge screen guard?

[AGalaxyuser]

No

[Samsung_Support3]

Dear Samsung Member,

Greetings from Samsung Customer Support!

Please perform the below mentioned steps to resolve the issue:

1. Restart your device. 

For further assistance, register your concern in Samsung Members Application (Open Samsung Members Application > Get help > Send Feedback > Error report/Ask questions).

Thank you for writing to Samsung.

Warm Regards,
Samsung Customer Support