If your WhatsApp number status has changed to NA after previously functioning correctly, there are two primary reasons to consider:
Deletion of the Number: This could mean that the WhatsApp number has been deleted from WA Manager.
Account Ban for Policy Violation: If your account or number is banned, it reflects a policy violation which requires an appeal to Meta for resolution.
you'll need to follow these steps to diagnose and resolve the issue:
Access WhatsApp Manager:
Tap on the WhatsApp icon.
Select "WA Manager". This action redirects you to the WhatsApp Manager where you can identify the issue at hand or visit https://business.facebook.com/wa/manage
Identify the Issue and Take Action:
If the account shows no number,it means number is deleted and now you need to permanently disable the channel and create a new WhatsApp channel for same number Register a New Number
If the account or number is banned due to a policy violation, an appeal needs to be made to Meta.