I managed to reproduce this with a payment failed notification, in dev, under special circumstances that I don't think they can happen here... but the notifications page did crash so it may be it.
I'll check payment failures. But, I am not experiencing this issue with my satwize account. I can see the activity there. All payments failed around 4-5 hours ago. I think they are okay now. Siggy47 account seems to have a different issue?