Why cannot I connect to the payment pages to complete a purchase?

[peegeestill]

Using Firefox on a PC. Account works on other devices but not the PC. Which setting is not set correctly? Access Denied page displayed.

[peegeestill]

Thanks for the information.  Did all suggested and still got the same screen on payment.

Used Chrome as well. Same result.

When I disabled my VPN software, ExpressVPN, the able to proceed.  The question now is what setting within the VPN software needs to be altered?