We regularly get support requests about the Smartlist window not opening.
The user will confirm that after restarting Dynamics GP, it is still not working, but it was working previously and they can't figure out what has happened.
Usually, what has happened is a result of a multi-screen environment, such as a laptop which is connected to one or more other monitors.
While it is not exactly clear what causes it, we believe that this happens when the user leaves the desk and takes the laptop with them to a meeting, etc. and then comes back later plugs in the monitors again.
Before leaving the desk, they may have had Smartlist open - probably displayed on one of the other monitors. Dynamics GP does not seem to reset the window location correctly (or perhaps only sometimes) and this results in the location of the Smartlist window being off the visible screen somewhere.
Then, when the user tries to open Smartlist again, it is actually opening, but it is just not within the visible area of the monitors.
If this is the case, the smartlist thumbnail will be showing as one of the open windows in the Windows taskbar:

So, how do we fix this?
It is actually quite simple, luckily.
Go back to the Dynamics GP Smartlist thumbnail in the taskbar and right click to expose the 'maximize/minimize' context menu, and click 'Maximize':

That should maximize the window back to where you can see it, but if the window was normalised again, it would revert back to the old location where it cannot be seen.
So, to completely fix the issue, simply click and hold the top bar of the entire Smartlist window (usually blue) anywhere next to (but not on) the maximize, minimize and close icons, and drag the window down a little.
This will put it back to a normalized state (i.e. the window is floating on your screen and is not mazimized completely) and importantly, the current location will be set to where you can see it.
So, the next time the Dynamics GP Smartlist window is opened, it will be visible again.