Hi @davy,
please register some new user and send the login details with your forum URL to info[at]gvectors.com email address to allow us to check it.
Thank you @davy,
If you don't have important information I'd recommend you to deactivate, then Uninstall (not a simple Deactivation, use the Uninstall button to remove all forum data). Then delete the wpForo plugin, search and install it again.
But I do not lose the forum doing so?
No but you should ALWAYS have a full backup (WP and DB) in any case. Any change (even an update) can ruin your installation. Does happen often but it happens.
If you have a Cpanel, a full backup takes 5 minutes to complete.
I uninstalled the plugin but the error ''add topic error'' remained...
It's a problem of your plugin