I am no longer able to payaccounts using Firefox

I am no longer able to pay accounts using Firefox, such as my supermarket and Govt motor vehicle registration, so I have to do that bit through another browser. It used to be okay, until recently. Supermarket is through direct debit, and car reg is by credit card. I can do the order without any problems, until the actual payment is tried, at which time I have to go to another browser and copy the URL at that stage, and pay it. What may be causing that? Thanks in anticipation. Cheers, Keith.