Big Sur

[Lulu KC]

I am having weird problems since installing upgrade over the weekend. I'm following all the directions to synch my iphone and macbook--but it's like they've never met each other. Has anyone had this problem and figured it out? All I can find is online is things I've already done that aren't working. I'll go to Apple support tomorrow if I can't get it figured out.

[CloudWatcher]

1. Big Sur works for me ...

Does the iPhone show up (in a finder window) if you attach with a USB/lightning cable? That's the easiest way for them to find each other. Though I do think the iPhone needs to be unlocked for the Mac to see it.

If the phone is unlocked and doesn't appear in a finder when attached with a cable, then the first thing I'd suspect is a bad cable and/or dirt in the ports on the iPhone or the Mac.

Only after it works over a cable, try to get it to sync over WiFi. It seems you do need to sync at least once over a cable before WiFi will work, see:
https://mashtips.com/backup-iphone-over-wifi-to-mac/

[Lulu KC]

2. I ended up calling them

It was a thing in settings on the iphone. For some reason, it now showed two possible macbook airs--one with sharing turned on, one not. I turned the other one on and it worked. No idea why it thinks I have two laptops but I'm not going to worry about it. Very brief chat with nice helpful person.