How often is the data updated?

Once a day, at application startup or in the background if the application is running.

warning

The main application window can be closed but if you fully quit the application from the system tray icon, the background process will be stopped.

A player is VAC banned but he still plays

A VAC ban doesn't necessarily mean the player has been banned from Counter-Strike.
The Steam API doesn't indicate which games a player has been banned from.

I got a too many requests error

If you see an error Steam API returned a 429 status code it means that the Steam API key used by the application has reached its rate limit.
That's why it's recommended to use your own Steam API key.