Due to a computer failure i've installed Adobe Premiere Elements 2019 on a new computer. When i try to activate the software with my 24 digit serial number it shows that this serial number is used on the maximal allowed numbers of computers and I should deactivate one of them, but I can't find how and where. I hope you understand my problem, english is not my native language but german.
You deactivate by signing-out via the help menu in the Editor application. You do this where you see your email address. If your previous computer is no longer working, you will need to contact Adobe directly.
Click the following link and scroll down the page to Individual. Then click “Sign in to contact us” It should be possible to start an on-line chat with Adobe Support. https://helpx.adobe.com/support.html
Make clear you are not looking for support for an older product, but need your activations re-set.