It's a different issue, but we don't know what the underlying cause is, yet.

(pasting part of my reply to a different thread)
It seems to affect only a handful of users. Some reported that switching to another browser helped, while for one it was persistent across two browsers. Some reported that trying again after a while fixed the problem. Unfortunately the issue only became apparent after regular office hours, our devs did what they could remotely, but they will have to continue the investigation first thing tomorrow morning.
For now, all I can suggest is:
1) try a different browser,
2) try again after some time,
3) use a credit/debit card directly, and avoid using redirect-type payments until this issue is resolved.
We're sorry about the trouble. :(
Are you using a proxy server, by any chance? The issue would affect the same user trying to use paysafecard as well, I'm afraid.
For now it looks like this occurs on a per-user basis. We're gathering as much information as we can, to help with our colleagues' investigation tomorrow morning.

It doesn't seem to be related to browsers, but is persistent per user, for a while. One user reported that they even tried to use Edge, with no plugins installed, and had the same problem.
Please share as much information in this thread as you can - any bit of info might point our devs in the right direction.
That being said, as shown by Barry, and at least one user from Support, the redirects can just start to work on their own.
We'll get to the bottom of this, but it will be very tricky.

I'll try to check back on this thread before I go to sleep, but I can't promise anything. I've got quite the headache, and need to help my wife with her work in the meantime. :)

Thanks, but I'm already the best! :D

We've added an option to do the redirect manually if you're stack on redirect page. Nevertheless we're still investigating the issue.