Nope, it's something on your side.
Bitrefill and many other places use myprepaidcenter.com for their mastercard prepaid cards.
Try a different browser. Also, they are US (possibly North America) only for some services. And they do block VPNs

https://bitcointalk.org/index.php?topic=5208530.msg61853963#msg61853963

Log out, log back in, try using a private browser window.

Heck, even a MC I got from a class action lawsuit was run through the myprepaidcenter.com site.

I also don't see that 866 number you gave on their site: https://myprepaidcenter.com/contactus

-Dave