Payment Gateway Error

A member was registering and buying a subscription, and they got the error in the screenshot attached. 
Notifications show this

PDT notification authentication returned unexpected result from payment gateway

His PayPal did go through, though.
I assume this is just a random error, but passing it on in case it's not. I am not attaching the details of the notification, but you can login and look at them.

PayPal Standard, Advanced, or Pro? We provide 3 different implementations. Does their basket still exist in CBSubs > Baskets? It's possible their basket expired before the payment came through if basket expiration time is set too low in CBSubs > Settings > Display > Baskets.

Gateway type is just PayPal. The basket is not there. Timeout is set to 3 hours.

Timeout is too short. I suggest setting it to 24 hours at minimum. If the user walked away and came back later to finish payment or if PayPal took too long it could cause the basket to expire before payment comes through.

Regarding that specific user edit them in CB > User Management and manually subscribe them so there isn't any further delay for them.

Some more info. We're in California (Los Angeles time), and the errors we've seen have  been for europeans. Maybe time zone somehow is involved?
On this case, it was 4 minutes from when they signed up (registered Joomla)  until the PayPal payment time.

All of the time calculations in CB and CBSubs are done in UTC. What you're seeing is localized for visual purposes. So payment came through 4 minutes after registration? Please PM (see link in my forum signature) backend super user login credentials and will take a look.