I created app at https://developers.facebook.com for WhatsApp Business.
To create permanent token (System user access token) , I'm trying to add System user at https://business.facebook.com/ but every time getting the message as You have been temporarily blocked from performing this action. Not getting why adding system user action is blocked for me.
Often Facebook/Meta block personal accounts or even commercial accounts to prevent fraud, spam and other unwanted behavior.
If you have a personal facebook account with zero data, friends, pics and you use it just to work plus you have changed contact data recently or something other, your permissions on the business manager could have been limited.
I leave a screenshot as an example
Check on "Account Quality" to see if that's your case. If so there you will see the steps required to fix it.