Youtube monetization copyright help

So I have an YouTube channel and my videos are monetized.

In some of the videos I use images from Wikipedia to help explain some concepts.
I make sure that the images I use are in the wikipedia commons and in the public domain

I got an email from YouTube about one of my videos which had a graph in it, which I was explaining. The email said they can't confirm I have necessary rights for commercial use of the content in the video due to the following reasons:

- the license you provided does not appear to have been issued by the appropriate rights holder for this content
- the audiovisual material you used was provided through a website whose licensing terms/terms of use do not grant you sufficient commercial use rights.

It then said I have to submit a reply showing an appropriate contract.

I then emailed back with a picture of the wikipedia license info of the image which said the image (of the graph) is listed in the public domain and is free to use for all purposes including commercial use.

I then recieved a reply saying they still haven't been able to confirm that I have the necessary rights to commercially use all the video material from the information I've given. They are then saying I need to provide documentation from a primary (original) source substantiating my claim that the material is in the public domain.

How to I move forward from here?
(sorry for the long post)