No mail displayed

Running any of the latest versions of eM Client, on iMac (late 2015) run by Monterey (all versions). When I start eM Client or try to re-install, it seems to load fine and the left panel is fine, it says how many new emails there are. But, no emails show up anywhere. Clicking anywhere makes it crash. I’ve had my hard drive looked at and all is well. Anybody else lost the part of the GUI that displays the list of emails and whichever one is open? Two or three different technicians at eM Client have given up. Help?