I've seen different things but non specifically this issue. 

My friend made a campaign and added us to it. 

Yes- I can click my characters in the my characters section. 

However- no one in the campaign can click on any character in the campaign itself. I can't edit or anything in the campaign. It feels locked. 

I have my other campaigns that work just fine. It is only his campaign that my character is that I cannot access it in the campaign. 

Does anyone know what the issue is?

Are you using the app or the website?

Is your username listed as the player for that character?