This might be due to canvas fingerprinting protection, you can let the site access the canvas from the icon in the address bar at the expense of exposing your browser fingerprint.

Hello zeroknight.

Thank you for your reply. I use standard protection. If I understand correctly fingerprinting protection can not be my problem. It's a curious problem. This qrcode does not work in firefox and it does work in edge. Other qrcodes work fine in firefox. Do you have any other suggestions how I can solve this?

Kind regards, Klaas

Does it still happen in a new profile? An easy way to test a new profile is to install Developer Edition and see if it happens there or refresh your existing profile.