I've never seen this in Thunderbird, but here's a tip: If a window seems to be hidden behind another window, you can re-size the front-most window by dragging an edge of it until you can see the hind-most window peeking out, and tap on the hindmost. It will come to the fore.

A lot depends on your sizing of your windows. You'll have little annoyances to cope with if you insist on running programs in full-screen mode. Make your TBird window occupy a smaller portion of your screen, and then click Reply, and make your Reply window occupy a slightly larger portion of your screen than the main window.

That'll do it.

Another trick you can use (when you have a window open and then you open another window that comes to the front) is press the Alt key and tap the Tab key. That'll switch the rear to the front and the front to the rear, and doing it again will do it again. <smile>

Hello @wisewiz

Sorry, have tried both of those as well as right click to move/re-size the reply window. None worked.

I'm having trouble imagining what you're seeing.

When you click Reply, is the main window set to full screen? Have you tried clicking the two-box icon just to the left of the X at the top right of your window, and then moving the edges of the reduced-size window to try to see the Reply window behind it?

Another idea occurred to me: With your main window open and a message selected, click the Reply button, and then if the Reply window is not right in front, minimize the main window by clicking the dash at the top of the window, to the left of the Full-screen/restored-size button. That will reveal any window that's hiding behind your main window.

This was the issue.

When you right click on the task bar and you can see both the Main Thunderbird program and showing next to it is the reply window message. I could only see the reply when doing that. It would not show up on eitier monitor, nor could I click on the reply message to move or resize.

It was not hiding but not behind the program. Had main minimized to about third screen size and reply, or write new, was not visible at any point. Tried several of your suggestions.

Right now it is working. All I did was keep switching program from one monitor to the other.

Now falls under category--It works--don't know why--don't play around and screw it up again--philosophy of Windows.