If your Facebook ad account becomes inaccessible, the icon will display greyed out with a 'null' icon 
over it, as per the below;
There are a couple of reasons why this might happen:
1. Your Meta account has lost the required access to the Ad Account
The permissions that give you access to your (or your clients) ad account have changed, and you no longer have access.
To rectify this, you will need to contact the ad account owner and review the permissions to update them so you can regain access. This typically happens when some setting has been changed by accident and simply needs to be reverted.
2. The Ad account is no longer 'Active'
Facebook has a status of 'Active' and Adpulse checks this status automatically every 6 hours.
Common reasons for an ad account being flagged as not active are;
Ad account closed or pending
Could be a policy violation. You can check the status of your Facebook accounts using the Meta Account Overview
Billing issues
Has not paid a bill, or the payment method has expired. Check the Billing status
How to resync the Ad Account connection
Once you can rectify the issue, you can manually sync the Meta Ad Connection here: Settings > Integrations > Ad Platforms
