ebay and firefox, paying with paypal doesn't work for me

So I'm running firefox 53.0.3 on ubuntu 16.04 and ebay keeps getting hung up on paying with paypal.

I click on pay with paypal, enter my paypal login and it gets hungup with a spinning circle.

It's done the last few times I've bought something.

I have to launch chromium, and it doesn't have a problem with this.