We're just fellow users here, swampdawg. If you've got an invalid serial number, you do need to work that out with Adobe.
Please indicate version of Premiere Elements and operating system on which it is running.
Nonetheless, please contact Adobe via Adobe Chat.
Click on the following link
When the link opens, click on "I still need help." to bring up the Adobe Chat. That is a very effective and professional group who should be able to help you.
I have attempted to pre-set the link for "serial number issues or activating my product"
Please let us know the outcome.