You may experience problems updating the game if you're having network issues, certain Windows-level problems, or if you have remnants of a previous partial install on your system.
If you encounter an error during an install or update, often uninstalling the game from Control Panel → Programs and Features, redownloading it, and restarting the install will solve the issue.
Make sure you are using a 64-bit client, as 32-bit clients are no longer supported as of the Core Set 2021 release. This was necessary to improve game and client performance and expand our supported platforms. Though impacting less than 1% of players, you can verify which version of Windows you're running in your System settings.