My mail app on a HTC one M9 cant access existing accounts (asks me to choose a provider)

[Android Central Question]

I have 4 email accounts set up on my phone, and out of the blue my mail app opened this morning saying "choose a provider"
if I go to accounts & sync in settings then select mail it shows me all 4 accounts and allows me to sync them
if new mail comes in it pops up the notification icon on the top of the screen
yet going into mail I get prompted to choose a provider like I have just asked it to set up an account
any ideas how to get around this without deleting and resetting all my email accounts ?

for info
OS : android 7 4.28.401.3

mail 10.70.1035099

 

[B. Diddy]

Welcome to Android Central! Try clearing the app cache for the Mail app in Settings>Apps​.