[@raamdev Member 15 years, 8 months ago]

I had the exact same problem and I tired everything that was suggested, including triple-checking that all my keys matched, the cookie path was set, and the bbPress Integration plugin was installed in WordPress. I still couldn’t get integration working.

Here’s what I did to fix it: I deleted bbPress, installed a new copy, and during installation entered the same database information as I used for WordPress (same database, same username/password, all of which are available in wp-config.php). I also filled in the various salts and keys as required.

That allowed full user integration on both a database and cookie level and now everything works perfectly. Single sign-on, one-time registration, etc.

Hope this helps someone!