Bill and I wanted to share an error message we recently encountered in case any members run across this issue.
If you try to comment on a post in main timeline (or a group) and receive the following error message, it is because you are not a member of that specific group...
For example, if you see a comment or photo/text post on the Home page timeline, and try to comment on the post or reply to someone who left a comment, the above error message may pop up. And trying again won't do anything.
However ... if you click on the group name and join the group, you can then comment, add posts, photos and interact with others in that group. Below example shows part of the post from home page timeline that Bill was trying to comment on the other day. He tried a few times to comment or reply to a comment, but kept getting above error. Then we realized he wasn't a member of USFRA News Room group, so he clicked on group name and joined, then was able to comment. Also note, if a post is a forum topic within that group, it would also show the title of discussion next to group name.
Hopefully this helps and feel free to add other error comments or questions in the comments, and I can add them to this main discussion going forward for other members. ~ j