It's possible that after installing the game, some files may be missing.
Therefore, try a files verification as outlined below.

Files Verification :

Step 1 :

To the right, you will find a small gear icon; click on it.





Step 2 :

Click on "Properties"












Step 3 :

Go on "Installed Files"
















Step 4 :

For finish "Verify the integrity of the game files"

The Summoners War team has recommended updating our graphics drivers, so why not =)

Graphics driver update :

Step 1 :

Install the GeForce Experience application if you haven't already and open it.





Step 2 :

Click on "drivers"




Step 3 :

Go on "Check if there are updates"





Step 4 :

If you already have the latest drivers,
you will see the message "You have the latest GeForce Game Ready driver".