Here is the first screenshot

And here is the second one. Permalink: /index.php/%year%/%monthnum%/%day%/%postname%

Why you've added index.php in permalink? This may affect wpForo.

Also You should add the trailing slash not remove. I don't see the trailing slash in permalink.

I´ve removed the /index.php/. The problem was still there. Do you have other options to fix the problem?

Here ist the current permlink: /index.php/%year%/%monthnum%/%day%/%postname%/

This is a site specific issue, I don't know what's wrong with your settings. I'd help you if you send admin login details to support[at]gvectors.com email address.