Paypal and 2-Factor Authentication

Am I the only person who has problems checking out on sites like Humble and Steam, when 2FA for Paypal is enabled?

It's a very consistent problem. Logging directly into the Paypal site is NEVER a problem, 2FA or not.

But there seems to be a lot of inconsistency in how different sites handle Paypal 2FA, and it seems as if many of them haven't updated or modified their checkout to use the most up-to-date paypal procedure, so that when 2FA is enabled, they don't know how to smoothly parse the login and pass things on to the next screen to ask for a code. Most of them seem to be trying, and then they get stuck. I've received various explanations for why this happens from Paypal support, or various denials and excuses or non-responses from various sites, but the problem continues. It's all very low priority to most, as if 2FA isn't a thing yet, when it is.

Thank god for Amazon Payments, because they recently enabled 2FA, and using it on sites like Humble or Groupees is never a problem.