bbPress.org

you’ll need to disable the bbpress plugin

https://codex.wordpress.org/FAQ_Troubleshooting#How_to_deactivate_all_plugins_when_not_able_to_access_the_administrative_menus.3F

Just deactivate the bbpress plugin for starters.

then you’ll need to figure out why it isn’t working for you.

I’d start by uninstalling bbpress, and reinstalling it in case there was a corruption as it downloaded

Then if it still doesn’t work, I’d disable all the other plugins and if it then works add them back one at a time to see which is causing the issue.

If not plugins, then I’d try switching to a default theme to prove that you WP installation is ok.

if all that fails, come back