Six things.
1. Please navigate to Dashboard > Users > Your Profile admin page and make sure the “Disable Visual Editor” option is not checked.
2. Navigate to Dashboard > Forums > Tools > Debug > Server admin page and copy your server information and paste it here. We need to see what versions of PHP, MySQL you use on your localhost.
3. Navigate to Dashboard > Forums > Tools > Debug > Errors and issues admin page, copy all errors and paste those here.
4. Navigate to Dashboard > Forums > Tools > Debug > Tables admin page, if you see any database error, click on the [Solve database problems] button.
5. Leave some screenshot of your topic/post editor, we need to see what’s going on your forum.
6. If the problem is not solved. Please install and activate the Duplicator — WordPress Migration Plugin, backup your WordPress site and send it to info[at]gvectors.com email address. We’ll check and find the problem in your website.