When you launch the game, the following notifications are popped up on the screen.
Recommended settings updated
Set optimal settings.
GPU driver version
In all cases click "No" and wait until the game starts loading.
If you see the process of loading shaders, as it's shown below:
You can and should pause this process since it merely doesn't affect your gameplay. Choose any Warzone mode you are about to play, then click "Pause installation".
Should you sport the next startup issue: "Unable to access online services" as shown below, keep in mind that this happens occasionally and you just need to reload the game from the launcher without closing your current game session.
The notification below: "Update requires restart" stipulates that you just need to click "Exit" and the game will restart normally.
If you want to play the game by means of the supported gamepad, keep in mind that before the start of the game you need to switch to "Controller" at the Input Device panel. If don't follow this procedure, the gamepad is gonna work in the game menu, but won't work in the game itself.
Pay attention that an issue in the game could be related to some temporary outages on the side of Activision itself. In order to exclude this case, please follow the link and check the status of their servers.