why after the update all the pages of the site became with an error 404! except forum pages
Your topic says nothing to let us help you. So please leave a forum URL, and a direct URL to the page with 404 error. In most cases, this could be a cache plugin issue or conflict with other plugins.
And don't forget to flush permalinks by navigating to WordPress Settings > Permalinks admin page and clicking the [Update options] button.
I returned the old version of the forum! why the new one does not have such a function for adding pages
Please update to wpForo 2.0 version again, then go to Dashboard > Boards admin page, edit the first board and turn on the option you are looking for. Here is the doc: https://wpforo.com/docs/wpforo-v2/getting-started/forum-page/turn-wordpress-to-wpforo/
enable WordPress debug, and check your error logs, you can check them from Dashboard > wpForo > Tools > Debug Tab > Errors & issues.
- Delete all caches in wpForo > Overview admin page, scroll down and find [Delete all caches] button.
- If you have a cache plugin, please delete its cache as well.
- Please deactivate current addons or update them to 3.0.0 version before updating wpForo to 2.0.x
- Deactivate Go2wpForo tool if you have installed and done forum migration
- Make sure you don’t have old forum template files in /wpforo/ folder of your current active WordPress theme directory /wp-content/themes/your-active-theme/.
- After the update to 2.0 Version, go to wpForo > Tools > Debug admin page, make sure there are no errors in Errors & Issues Tab
- Then go to Database Tables tab in the same admin page and check the database issues.
- After the update, please delete all caches and purge CDN if you have.
