Cheers Katya,
I have done this many times,
last test, this is what I done
entered sender id and api key and saved, created a new screen, dragged 2 components to screen and saved,
checked app settings, push notifications details where in place, they where, saved app, clicked return to project list.
reopened app, the new screen and components where saved but not the sender id and api key, they are now blank, the platform is not saving these details, is this a bug, I have tried this on other backup apps and the same result!