I had my site configured to accept payments from PayPal, Amazon, and Authorized net. Everything was working great. Last week, I upgraded to Magento 2.3.1 and installed Affirm as a payment method. I tried switching to a basic Magento theme to see if it was a bug in the theme, but it has the same issue.
After that, Affirm is the only payment option.
As far as I can tell, these other payment options are still enabled.
I tried flushing the caches, I've tried recompiling the site. Still no dice.