Firstly, Can you access the game after the main menu? And can u Press Escape and go to any of the options?
Try to provide a little more details about the issue.
Try the following methods :
1) Disable and Re-Enable your Mouse from your PC and restart your PC
2) Try creating a new game if can't do in-game then delete your current save file from:
C:\Users\(User Name)\AppData\Local\ShopSim\SaveGames
3) Try Re-installing the Game.
(The Second Method should Most probably work and is the best fix)