Game gets to start menu. Starts the update. And keeps updating and checking files. But won’t get past it.
Try Options and the Scan and Repair. If needed then clear the Cache and Reinstall Battle.net App
Lastly, if all of the above fails then you're left with reinstalling the game files (89GB). Further, if you modified any of the game files including any Configuration files this too can cause a corruption. If you modified the Config file then move it from its folder and run the Scan and Repair.