Armor Non-Proficiency penalties are being applied to proficient characters 5e D&D

In my new 5e D&D campaign, I have a heavy fighter that is getting penalties for Non-Proficiency with Chain Mail armor. He has "Armor: Heavy", light, medium and shields in his Proficiencies.

I have added and removed his heavy proficiency, but He gets disadvantage constantly with the following message:

[SKILL] Athletics
[PROF]
ARMOR NON-PROFICIENCY
[DIS] [DROPPED (9) SECOND]

Please see uploaded images.

How do I fix this?

If you click on the gear button next to the AC window, you can toggle whether PC is proficient with the armor they are wearing. This is not changed automatically; and the sheet assumes that you are proficient by default, so it must have gotten toggled off accidentally at some point.

Regards,
JPG

Thanks!!

That fixed my issue!