I am adding to my previous comment as my guild appears to be running into a major bug, or if it isn’t a bug it’s certainly not intuitive as to how to solve the problem. I have taken screenshots as well to show that all of the typical conditions to be able to play heist are met.
Yesterday when I had started a heist I had set it to private and invited several friends and guild players, a few were able to join but others were not; at first we chalked it up to maybe they didn’t have enough heroes or something of that nature. Today one of my guild mates tried to start a heist in private mode, sent an invite to all guild players including myself. I could see the invite, I had 6 tickets, and they were the only player in game so I most certainly had enough heroes to play. When I went to the game through the invite there was no option to ‘join’, I tried going to the game through the heist building with the same result. Just to make sure it was just this game I tried going to another public game and he join option was available. No one else that was invited was able to join the game either. I will include picture below to show all of what I have outlined here
This shows that I had received the invite
This shows that there was no join option
This shows that the game was showing up in the heist building, and that I had several tickets and a free play available
This shows the guild chat where other members were also having the same problem.