AUTH_UNAVAILABLE on placing order error

When trying to place an order yesterday I received the error type “AUTH_UNAVAILABLE” back from Smarkets API. I’ve not received this error before and seconds prior to this I was able to successfully place an order. I can’t find anything in the docs that explains why I got this error, it did, however, cost me some money so I would like to know how to resolve this issue going forward?

Did you ever solve this issue?
It happens to me occasionally and I dont know why.
Everything can work fine for an hour and suddenly I get this error