https://www.pcgamer.com/treyarch-working-on-black-ops-4-battle-royale-pc-beta-crashes-and-aim-tracking-bug/

If you've been playing the beta for Call of Duty: Black Ops 4's Blackout battle royale mode, you may have experienced crashes, or problems launching the game. In an update posted yesterday, Treyarch said it was looking into it, alongside other issues such as crosshairs tracking enemies through walls.

In a Reddit post, the developer said it was "tracking a handful of reasons for crashes and issues launching the game across various PC setups". Hopefully they're fixed today—the beta only runs until 10 am PT/1 pm ET tomorrow, September 17.