Apple's having big iCloud issues tonight. If you can't get your mail, or sign into iCloud, or synch your calendar... it's not you, it's them.
Major Apple iCloud issues September 29th, 2020
Why Don’t Photos Sync between my iPhone and Mac?
If you took a picture with your iPhone, and expected it to land on your Mac, but it didn't-- here's how to fix it. iCloud synching requires WiFi.