Steam:

• Restart your computer and launch Steam
• Next, you can either right-click the game in your Library, or click the gear icon from the game's Library page on the far right
• From the drop-down menu, select Properties...
• Select the Installed Files tab and click the Verify integrity of game files button
• Steam will verify the game's files
• This process may take several minutes

Epic Games:

• Open the Epic Games Launcher.
• Find the game in your Epic Games Library.
• Click the three dots on the right side of the game line.
• Select Manage.
• Click the Verify button.
• Wait for validation to complete.
• It may take a while to verify all your files.