Another multiplayer question

Hello, my partner and I recently both got AOT2 and were very excited to get into it. We have played the first couple missions for ourselves until we could do the distress call. I have tried joining them when they invite after doing distress call and I have also tried joining through SOS but neither of these are working. I am reading mixed things online and was under the impression I could play their missions regardless of my own progress as long as I am okay with my story not progressing and only theirs being the one that progresses. Any tips or knowledge on how to do the story mode with them would be greatly appreciated. This is all on PC btw.

TLDR: 2 new steam players would like any workaround or ideas to play story mode together, or does one player need to beat it solo so they can help with distress calls?

Thank you