This has happened to me in the past and usually I discover the SF window is lower than the taskbar - in other words, it’s positioned off-screen.
Here’s how to fix, if this is your situation:
- hover over the SF icon in the taskbar so the preview window opens
- right-click the preview window and choose MOVE
- Press the UP ARROW KEY*** on the keyboard to start repositioning the window
- At this point your mouse is now locked to and is controlling the title bar so you can move your mouse to reposition the window
- Press ENTER on the keyboard to release the lock once you can see the title bar.
*** or DOWN/LEFT/RIGHT as needed based on what works
Hope this works and helps!
