Note that I deleted the other copy of this post. Please just post a question once.
Ok – assuming the url is being created OK which I feel sure it is – then something is causing either redirection or is scrambling the WordPress rewrite rules.
So first try forum admin > integration > page and permalink: Is the correct page shown at top and assuming it is click on the update forum permalink button half way down and then see if that helps.
If it does not then what about topics and posts? Are they loading the correct ‘pages’?
And if not – do you have any redirection plugins active? Yoast SEO plugin? Any caching plugins?