Save your description and your pictures to your desktop.
Then close the computer and take a walk in the sunshine.
When you get back, start the listing all over again. The glitch will probably have resolved itself by then.
Hmm. Does the email address you are trying to load match the email address for your Paypal account?
Do you have an earlier successful listing that included the email address?
You could try going to that listing, using Sell Similar and change everything in that listing to the one you are trying to upload.
And add the accepted listing as a template. That may prefill the PP address section.