4.8 will not integrate with vbulletin 3.7 series that is for sure it is way to old a software it will not even work with 3.5 series
If it does not authenticate your users when you login then it is definately too old. 4.82 was right around when we added
vb 3.5 series support. You would want to check that your database settings where correct to connect to the proper vbulletin and see if you can authenticate the user if not then you definately need to upgrade.