I feel silly asking this and even more silly to have this problem. I have a android project that has been executing fine until now.
but a couple of days ago, without
I'd tried everything on here and was surprised by the overwhelming acceptance of the top answer
Restart the device
then I realised, "this is a development phone, stop treating it like a business's server", and proceeded to restart.
Worth risking an answer to endorse this solution as a last resort.
My outcome- the app quickly, but quietly died. Result ! :(