macOS Big Sur (11.6.1) on a late-2013 MacBook Air.
iOS 15.1 on an iPhone SE (1st generation)
AirDrop works from the MBA to the iPhone, but not from the iPhone to MBA. When trying to send a photo from the iPhone to the MBA, the MBA appears on the iPhone as an AirDrop destination (i.e., the MBA is "seen" or "discovered"). When selected, the MBA icon shows "Waiting," but the transmission doesn't occur.
In the opposite direction (MBA > iPhone) AirDrop works correctly. Both the MBA and iPhone connect and operate correctly, and both are connected to the same wifi network. Bluetooth is enabled on both, and on the MBA sudo pkill blued has been run in the Terminal, and /Library/Preferences/com.Apple.Bluetooth.plist has been trashed (and automatically recreated).
Until last week, AirDrop worked bidirectionally, as it has on these two devices for years. I cannot identify a specific update (on either the MBA or the iPhone) after which AirDrop failed.
I've restarted both machines, force-restated the iPhone, and signed out of iCloud and then in again on both. No change is noted.
What else might I try?