Sometimes, it's just restored down real small in a corner.  If you can spot where it is, it's as simple clicking on the maximize button.  Otherwise, you can open Task Manager, right click on the Process for Lacerte, and select Maximize.

This is the classic sign of Lacerte being on a monitor that does not (currently) physically exist.  Generally your screen set up may have changed, but not always.

Press the ALT-Spacebar and you should see a small window popup with among other items MOVE.

Use the ARROW keys and select MOVE.  Hit the ENTER key one time.  Use the arrow keys (up\dn\L\R) to bring the window back on the screen. 

HIT the Lacerte window is near the popup, so if it displayed on the top right, use the down and left arrows.

https://proconnect.intuit.com/community/lacerte-tax-discussions/discussion/lacerte-window-appears-of...