Sorry, nobody at this user to user forum is going to be help with a serial number activation issue... that is only Adobe
You are going to have to go back to Adobe for this
Help for Download & Install & Setup & Activation
As John T correctly states, this is a User to User forum. There is rarely any Adobe presence here, and when there is, the Adobe Staff member responding is a software engineer with the Premiere Elements Team, and not a Customer Support person. That means that they know the code in the program (likely wrote part of it), but that beyond the inner-workings of the program, have no direct contact with Customer Support, which might be in a different country, from the development/engineering office.
That line about "returning the software" is a puzzle, as you seem surprised by that reply.
I would reconstruct the events around your purchase of Premiere Elements:
- Did you purchase directly from Adobe, or from a certified reseller?
- It seems, from the other comments, that you purchased a download version of PrE. Is that correct?
- As Adobe offers a 30 day, money-back guarantee with their software, did you ask to return the product within 30 days of purchase?
- If so, was your credit card credited for that "return?"
- Do you still have the invoice for the software, or a copy (digital or physical) for that purchase?
- Do you still have your credit card statement for that purchase?
- At Adobe.com, when logged-in with your Adobe ID, do you see the purchase of PrE in your software tab?
- Is that where you attempted to download and install PrE from?
Armed with the answers to those questions, I would contact Adobe Customer Support, and probably via telephone, and discuss your issue with the support representative.