It could be a theme or plugin issue
Themes
As a test switch to a default theme such as twentyfifteen, and see if this fixes.
Plugins
If that doesn’t work, also deactivate all plugins apart from bbpress and see if this fixes. if it does, re-enable one at a time to see which is causing the error.
Then come back
Activated 2019 theme. Problem persists.
Deactivated all plugins except bbpress. Problem persists.
the link all looks good
couple of other suggestions
1. This could be an issue with your rewrite rules. To fix this try resetting your permalinks. In your WordPress Administration Screens navigate to Settings->Permalinks, select a different permalink structure and save. Then select your preferred permalink structure and save again.
2. A reinstall of bbpress. You won’t lose any data if you decactivate and then delete the plugin.
Done the resetting permalinks, then deleted and reinstalled bbpress. Problem persists.
ok, sorry nothing else I can suggest
It seems to be an issue finding all the replies. In the database all those posts have the type “reply” as post_type. I don’t get it. The link matches the format for forums and topics, which are able to find all the posts just fine.
…/wp-admin/edit.php?post_type=reply
In addition to this, all the reply post authors are being input as 0, which makes them anonymous. I have that unchecked in the settings.
Is there a way to permanently delete bbpress and all its contents so I can reinstall fresh? EDIT: I found the answer to this question. https://codex.bbpress.org/getting-started/installing-bbpress/deleting-bbpress/
Never mind. I can’t even delete it to start over. The bbpress reset in tools does nothing at all.
I have not been able to delete bbpress. The reset tool does not work.
ok, I think your site has issues.
