I just checked at the different tests you made on your site.
The one on “second qr code test” page is working well, what tells me the plugin is functionnal, so I looked at “test QR code” page, indeed the image generated is all white.
So I have verified the parameters, and there is an error on your color parameter: the content is ”#2198DC” with the quotation marks, which shouldn’t be like that, you should delete the double quotes of the parameters.
When I manually deleted them and retested the generation, it works fine. Try it and tell me if it’s ok.
Thank you, best regards.