This is not Adobe. We are Premiere Elements users trying to help other Premiere Elements users with their Premiere Elements workflow.
From the description of your problem, this sounds like a matter that Adobe needs to handle. Please contact Adobe via its Adobe Chat at the following link
I have pre-set it for "Serial Number Issues or Activating My Product".
After the link opens, click on "I still need help." to bring up the Adobe Chat.
The Adobe Chat group is an excellent group of reps who should be able to solve your issue professionally and quickly.
Please let us know the outcome.
Before you contact Adobe Chat, please double check that have located the correct serial number, typically on labels on the box that houses the envelopes with the installation discs.
This is a user to user forum, not Adobe support... but, are you sure you are entering the serial number and not some other set of numbers and letters?
Select a reason, then click I STILL NEED HELP to activate Premiere Elements chat
Grin... slow to click !!!