Do you mean the button showing two squares overlaid (restore) does not change into the single square (maximize)? Or that the size of the restored window is the same or larger size than a maximized window when you use the button?

If the window is resizable, you can use the spacebar trick:

• Press Alt+Spacebar to summon the window control menu at the upper left corner of the window.
• Click Size or tap the S key, then tap the right arrow key to select the right edge of the window
• Press and hold the left arrow key to reduce the window width, and press Enter to complete the change and exit out of resizing mode
• Call up Size again and repeat with the down/up arrows

I mean the 2nd. Size of restored window is same size as maximized window when I use the button. Tried you “trick”. “Size “ is not in bold and does not respond to being clicked on Pressing the “s” key closes the window in the upper left hand corner.

The two normal situations are:

• Window is maximized: Restore is enabled, Move and Size and Maximize are grayed
• Windows is resizable: Restore is grayed, Maximize is enabled

It would be strange if you have a mix, where you could Maximize but you could not use Size.

Maybe that is possible in a popup window? In that case the URL in the address bar wouldn't be editable. Does that seem to be happening?

Make sure Firefox isn't set to run in Full Screen mode (press F11 or Fn + F11 to toggle; Mac: Command+Shift+F).

• https://support.mozilla.org/en-US/kb/how-make-firefox-and-websites-go-full-screen

Try to rename/remove xulstore.json in the Firefox profile folder with Firefox closed.

You can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page (Root directory).

• Help -> More Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

Thank you. Display was not exactly as you described, but I was able to figure it out and resize the window. Thank you. Most grateful.