You only briefly mentioned PayPal, but I'm genuinely curious; did you look into PayPal Adaptive Preapproved Payments (optionally with the embedded flow as seen here: https://www.x.com/sites/default/files/paypal/imported/lightb...)? If so, why did you decide this was not for you?
Yes, I could've imagined a better way to start the week.
We had some errors on our API's being returned in the morning (7-10am GMT) followed by prolonged issues with Instant Payment Notification messages not getting sent out to merchants.
Things are looking up again and Instant Payment Notification messages are currently going out. We're now working on reducing the backlog of messages.
This is expected to take the next 24 hours before we're fully caught up.