Yes, I am having the same issue. I have spent many hours researching this.
I have gone through extensive troubleshooting in which I disabled all plugins, scratched my database completely of all bb_ and bp_ tables, removed all bb_ and bp_ references in wp_options, reinstalled BuddyPress – and still not working.
I also reviewed and verified my bp-config and wp-config to verify database, password, db_charset, db_collate settings.
I have also looked at all of the solutions in the following links:
https://buddypress.org/community/groups/how-to-and-troubleshooting/forum/topic/forums-bug-there-are-no-posts-for-this-topic/#post-82249
https://buddypress.org/community/groups/how-to-and-troubleshooting/forum/topic/forum-does-not-work
I am down to the option of completely starting from scratch and installing a clean install of WP, and BuddyPress. This will take some time…
I do think it is a bug.
If you find an solution, please post it. Thanks.
Add me to the mix on this one. Brand new installation – real generic, no funky plugin, nothing out of the ordinary. Everything seems to be working except for posts in the forums (both from within a group or from the /forums/ location).
If it helps anyone, I notice that once I click the button to submit my post, the url it is trying to reach ends with // instead of a single /. Perhaps helpful?
Sigh…
Go to a group that you have created, your the admin of the group. Go to the Group’s Admin –> Group Settings.
Now see where it says “Enable discussion forum” box? uncheck- recheck about 4 times, then click save at the bottom and try to create another topic
That, my friend, is just silly. Perhaps it may work, but you would think that with so many people having this problem that it would be addressed in the source code somewhere. But, alas, such is the nature of free and open source software. Besides, who wants to build a project, or even something bigger like a brand, based on technology that requires three or four clicks of the on/off switch to finally kick it in gear?
I had to move on to something that worked.
sjt
So I tell you a solution for you to try, and you call it silly? Do you even know why I told you to do that? Have you even tried it?
The most likely reason that it’s doing this is because the forum ID is not entered. Unchecking, and rechecking, re-enters the ID.
So before calling it silly, actually try it 
, and if it does not work, thats not a problem, we can move on to solving your problem.
I found a solution to this problem here:
https://buddypress.org/community/groups/how-to-and-troubleshooting/forum/topic/bbpress-posting-errors-missing-database-tables/
Check your database tables and make sure all of the necessary tables for bbPress have been created in your installation. In my case I was missing the bb_post table (the one involved in actually posting a topic) – it was failing to install properly due to an error in MySQL syntax – all explained in my thread. By downgrading my MySQL version I was able to install bbPress succesfully – the missing table (bb_post) was created and I was then able to post forum topics in my groups without any error!
Yes, Virtuali, I did try it. Several times. And yes, I checked all the database tables to verify through direct observation that the “switch” was being thrown. And yes, just like MANY others, that did not solve the problem. Like I said, silly…
Well, @hnla might be more insulted when you call that “silly” since she was the one who provided that solution that worked for many people.
Have you changed your database info ever? Changing database info can cause this to happen.
@sjtryon please understand that on a community forum such as this where people attempt to provide help to others on their own time for free as it were it does come across slightly rude to make remarks such as ‘silly’
Now I must really get my avatar sorted out as clearly I’m simply posting in far too feminine a manner 
@hnla how about Boris from Rocky and B. Show? Or, fellow Brit, Bond, James Bond?
@mercime after lengthy and careful consideration I would have to say Bond, it was close though
@hnla I’m going really off-topic now. heads up on which Bond, @finni3 has Sean Connery
@mercime darn it, it will have to be pierced brosne man then -always thought he did quite a good job in the part.
What is this?!? I got dibbs @hnla! Stay away! Have you considered https://i.imgur.com/0Ff4x.jpg , if you want an agent avatar that is?
@finni3 no I’m trying to get away from this impression I’m a bird! maybe I’ll go with Napoleon Solo he was quite cool
About Solo: ” Like his partner he has a wide knowledge of English poetry. Unlike his partner he lacks a broad knowledge of science and technology. ”
I’m having this same issue. Is there any way to solve this without going into myphpadmin? This has a solution:
http://wpmu.org/daily-tip-fix-for-buddypress-group-forums-error-when-creating-a-new-topic/
but I don’t know how to do it. Is there any front end way of fixing it? I tried the clicking unclicking thing but it didn’t work.
thanks @ngoegan, this works.
