I had the same problem and the first response from Digitec support was the Adobe redemption site described above. But that didn't work either. Support then sent me a different key and a corresponding serial number "after consulting the product expert". Then it worked.

Good evening Christophe
I have now also managed to download the software and activate it.
1. copy the code you received from Digitec.
2. then open this page in your browser: https://www.redeem.adobe/elements
3. existing Adobe customers can then log in directly or you can create a new Adobe customer account.
4. then enter the voucher code you received from Digitec in the field.
5. now you can download Adobe Photoshop Elements

Many thanks also to Christophe 😊

Good evening Raphael,
I've also had trouble activating my licence. Adobe has completely changed its system and the delivery email from Digitec is incomplete 😢. In fact the code received is an exchange code and to use it you have to go to the "https://redeem.adobe.com/elements" page.
However, I don't know if you need to create an Adobe account beforehand.
I wish you good luck.