Cannot access email messages via Mail and Time Machine in Catalina

With the Mail program running I select Enter Time Machine. The screen changes somewhat and goes to a smaller window showing my email accounts on the left, but in the space on the right of the window where I assume messages should show up- there is nothing. All of the buttons are grayed out except for the Cancel button. The timeline along the right side of the screen shows backup dates and times, but I cannot select any of them. Time Machine works fine with my documents and applications. I've waited for up to 5 minutes to see if anything changes but it hasn't. This is a new iMac I am using, and when I set it up I told it to use the most recent backup from my old machine, with my new machine. Time Machine is making regular backups, but I simply cannot access any email messages at all. I've tried restarting the machine, ejecting and hooking the external Time Machine drive up again. Everyone thing I've read says to open mail, select Enter Time Machine, then scroll back to the desire date. I cannot do that.

rtvman