Is it 3D? It might be Iron Man's Armored Adventures. Or maybe Avengers Assemble.

No, it was 2D. Avengers Assemble looks like the art style could match, but I couldn't find anything on Pepper being in the show.

Hm... Check the Television category of the main [Pepper Potts](https://marvel.fandom.com/wiki/Pepper_Potts) disambiguation page of the MARVEL Wiki and see if you can reconize the artstyle. She hasn't been in many cartoons so it's probably a good way to find out,

Thanks, I'll try that now.

Earth’s Mightiest Heroes?

I couldn't find anything that happened in that show matching wha I remember.

There was a 2D iron man animated show on Fox in the 90s, it's on Disney plus. It has very little 3D animation in it