cannot quit mail on my 2015 MacBook pro.

I'm running mac os Monterey ver. 12.7.6 ...

A message reads mail was interrupted and need to quit mail, but the quit button is greyed out. I tried clicking and holding on the mail icon on the dashboard which brings up another quit button, but clicking on that doesn't work either. Also, if I go to my mailbox my new mail appears in the sidebar but the message itself won't show when I click on the particular message. So the main problem seems to be quitting the mail app in order to reset the proper flow of info.