apple mail for MacPro Monterey 12 does not open the mails, only the titles

Hello. The e-mail titles are visible at the left, but the content of the mail stays invisible all the time.

Only when I reply to the sender, I can see the content of the incoming e-mail.

The issue is only on the MacPro Monterey 12 with apple mail.

On my iphone it works well.

I woud like to keep working on Monterey a little longer, is there a way to avoid the mail issue?

Thanks for the help.

Many regards

Els