I just recently bought the diamond elite membership pass but it was through NJ six flags can I use my voucher here in Valencia or do I need to activate it in NJ ??

If I buy a Season Pass at one Six Flags park, can I activate it at another? No. You must activate your Season Pass at the park you purchased it from. For example, if you purchase a La Ronde Season Pass you cannot use it at any other Six Flags theme parks until you first pick up your Season Pass ID card at La Ronde. That's straight from their website. Your question had me curious too. Hope this helps.

Nope...two different states.

I would talk to the person at the membership area and see what they can do to assist you..I'm thinking if you haven't then just register and activate it there in valencia