Error when setting up website payment NVP/SOAP API

[Jordz2203]

So im trying to accept payments on my WHMCS website. I set it up with NVP/SOAP API and when I try buy something with another account to test it I get this error so do customers "Things don't appear to be working at the moment. Please try again later." 

Screenshot  - https://gyazo.com/c7d9b601c6ace5bd61067382599c10d8

[Jordz2203]

Edit: Yes all my API info is correct

[LeighVH]

I'm having the exact same problem.

WHMCS are saying it's paypals problem. All the info is correct, encoding is set to UTF-8

Tried everything other people have recommended and still will not work.