why doesn’t the mail app on iPhone XR load emails?

The mail app on my iPhone XR is not working. It worked when I first set it up, but then stopped. Rather than load messages from various account, the error message “multiple account errors” comes up at the bottom of the screen. I tried deleting and re-adding the accounts and it still won’t work. I also tried it using various wifi servers as well as the server provided by my carrier. Is this something that others are experiencing? Does anyone know how to fix it?