I just set up 2fa for my Epic Games account and I had to mess around with the page styling to get the QR code to scan properly. Here's a screenshot of what their page looks like:
As you can see, there is a rounded, padded light-grey border around the QR code. I had to turn off the rounding and either the padding or the border itself in order to get the 1pass extension to recognize the code.
Side note: if a less technical user were to encounter this problem, is there a way to give 1pass the manual entry key and add the 2fa code that way? I looked for it but couldn't find it in the extension.
1Password Version: Not Provided
Extension Version: 1.16.2
OS Version: Firefox 69
Sync Type: Not Provided