Solved. I edited this. What an idiot. I have two monitors. One was off. The last time I used mail I'd moved the opened email to the 2nd monitor. The mail program continued to open the on the 2nd monitor. Using the Mail program with the most recent version of MacOs. I receive email fine, but when I try to reply the reply window doesn't open. Nothing happens. This is happening in all of my email accounts (apple, gmail, and aol). I can use the browser based version of mail from my icloud account without a problem. I've tried shutting everything down and restarting the computer 2 times, so that doesn't fix it. I also don't see any warning icons for any of my accounts. Anyone have a clue what might be happening? Thanks.
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