buttons not working in separate message window in Mail on MacOS

Same here. Already, tried restarting Mac, used disk repair tool, still no luck.

Please help.

Just found that, when a separate message window is opened, if you go to main menu - view - customize tool bar, then delete all reply, reply to all, forward buttons, then add them again from the customize tool bar back into the message window the buttons work. BUT, once you close the message window and open it back, they are not working again (greyed out).

Seems fixed in latest Big Sur beta.