Purchase from Bonobos failed with unexpected web page at checkout.

[Dyn0saur]

Hello, I'm new here and I'm not sure I'm in the right forum; but I didn't see a matching label. Here's what happened:

1. I tried to buy a product at Bonobos.com using PayPal.
2. From the site's shopping card I selected Checkout.
3. An unexpected website opened
   1. URL:<removed>
   2. Error message: Invalid request.

Here's my question:

1. What happened?
2. Why did it happen?
3. What can I do to keep it from happening again?

Thank you,

Mac mini M1, Browser: Brave,