Apple Watch won't unlock my Mac after upgrading to iPhone 17 due to iCloud

I recently got the iPhone 17, and had to pair my Apple Watch to it. I also have a 2017 MacBook Pro and have been using my watch to unlock it for years. Since getting my new phone, my watch hasn't been able to unlock it. When I've tried to turn on the "Use Apple Watch to unlock your Mac" setting, it says "Your Apple Watch must be signed into iCloud to allow it to unlock your Mac. You can sign in using the Apple Watch app on your iPhone." When I try to do that, I can't find anything regarding my iCloud on the app. I was able to sign in to iCloud on my watch itself, but it didn't seem to do anything. I'm basically at a loss with this, and I haven't been able to find anything online about it. Anything helps!