Redirect to another website

I am using the newly released version of Firefox on two of my desktop computers, both are running under Windows 10 Home. I cannot see any differences between their settings, one is on a Lenovo desktop w/ Intel Core I3 cpu, the other is on an HP Pavilion desktow w/Intel Core I3 also. My issue is that when I make a purchase on eBay, the syster transfers me to the PayPal site to make payment. With the HP machine, everything is fine, it goes to PayPal, and payment is made. With the Lenovo, it transfers me to the same pop-up page, but all I get is an everlasting circle running on a black background. In order to make payment on that computer, I have to copy the url info, open Chrome browser, paste the url into that browser, and continue from there without incident. I’m sure the problem is with some setting, but I cannot find what to change to fix it. Help!