For those of you that use split or dual screen while using ANSYS, please remember to drag the extended Workbench screen back to your laptop monitor before disconnecting the extended screen. If you forget to bring Workbench back to the main screen and disconnect the monitor, the next time you launch Workbench without the extended monitor it will not appear on your laptop screen.
Solution to this is reconnect monitor and drag Workbench back to your laptop screen.
You can fix this by clicking Windows key+left button on your keyboard while the ANSYS window is open.
Source: Mr Chai Koon Hoe