After I recently upgraded my pp to the latest version 4.8.2 from an old 3.1.1. Everything but the cookies worked. And I tried for many hours to get the cookies to work with a newly updated vbulletin. 2.2.8 to 3.0.2. I did the whole nine yards - in this thread : vB3 Integration FAQ
and still no go. The cookies would not work - to my frustration. I tried every possible combination of the variables and was stumped.
So, finally I got into phpmyadmin and started looking around - amazingly, the table - "settings" was incorrect. why it did not update is beyond me. But I had to change two things and now it looks like the cookies are working.
#1 - Since I changed the vbulletin to a different database (and the pp update program didn't reflect this) even though I think it is supposed to in the 2 php files indicated in this post: renamed mysql database during vb upgrade and have config question
I manually changed the URL in line 7 of the pp "settings" table. This now pointed to the correct vbulletin URL.
#2 - For some reason during the upgrade - this "settings" table did not update the "User Registrqation Settings" on line 41. I changed it from vb2 to vb3.
I don't know if this normal and would like a pp support team member to comment on this. And advise if this is a fix - don't change anything until a support member verifies this is acceptable practice. But if this is happening to someone else as it was me, you might just have a look see at your settings table. This may be a troubleshooting step that helps in getting your cookies working.