The MacBook Pro is running v10.11.6 and the iPhone is on v11.1.2, both devices can see other people's MacBooks and iPhones, but these particular two devices just won't see each other.
Both devices are set to AirDrop ‘everyone’, the iPhone is logged to an iCloud account, the Mac is not signed into any account (it's a company device)
I've tried all the usual ways on both devices, rebooting, resetting, etc. but still no luck.
I thought maybe there's something wrong with the bluetooth, but I can successfully pair the Mac & iPhone to use iPhone as personal hotspot.
Then I tried the wireless diagnostic tool. I find that the AWDL (Apple Wireless Direct Link) in the monitor window does show the correct peers count (I mean if there's only the Mac and iPhone, and I unlock the phone, peers count would show 1; and it shows 0 if I lock the phone), which indicates that the Mac does see the iPhone after all. It just won't show up in AirDrop (Mac cannot see phone, phone cannot see Mac).
I should add that, randomly, the Mac and the iPhone can see each other. I've tried, like, thousands of times, but, it only happened exactly 3 times, and when it does show up, I can successfully transfer files (only for 3 times).
How could I debug this?