I'm sorry to say that push notifications may well be offline for a while.
We recently (beginning of May) transferred our app to a new company, Weather Gods ltd. The app transfer using the Apple transfer process didn't go so well and we were left with our account in a limbo state.
This was fine whilst we didn't need to make any updates and we raised a case with Apple to resolve the problem. This is still ongoing.
Unfortunately, our push notification certificate has now expired and we are unable to link to the new app until our app transfer problem has been solved.
I have escalated with Apple, but these things take time unfortunately.
It's possible that something might cycle through and allow a new certificate to talk to the old app ... but I'm currently just seeing failures to send pushes.
I'm really sorry about this and hope to resolve it as soon as possible.