This tool will let you look up Users and Specific Ads ran through the Real Geeks Facebook Tool.
Facebook Admin Tool Link:
https://fb-ad-tool-api.realgeeks.com/admin
Make sure that you have active session on http://fb.realgeeks.com/ or the admin link will not work.
This will give you the ability to look up specific users and ads without having to add yourself to the client's account.
You can click on the details to see the errors they are getting and which pixel those ads are trying to pull from so you can compare that pixel to what's in MCP and what they have in their Business Settings.