As the title says, when I join a new community using the Boost app, and then later try to go to that community, I'm getting an error message "404 couldn't find community". Any community that I had already joined before using Boost, I'm not having this issue.

Edit: I did find a workaround for this problem. If you click on the three dots at the top of the community list, then click on Refresh. This seems to fix the problem.