The problem is that the program doesn't have the necessasry permissions to run.
This can easily be fixed by navigating to:
"C:\Program Files (x86)\Steam\steamapps\common\Tower Unite\Tower.exe"
Then right clicking on said .exe file and click on the "Properties" option
In the Compatibility tab click on "Run this program as administrator"
Now the game will run with all the necessary permissions that it didn't have before.
If a popup appears saying you need to enter an administrative password to launch as an admin that means your account is just a standard user, which you might wanna look into changing because that can easily prevent this from happening again later with other programs.