Apple has built a lot of proximity tools into iOS and macOS, and they’re great when they work. But when they don’t work, it’s leaves you scrambling to find an alternative. If you’ve ever used Handoff, Apple Pay, or AirDrop, you’re using a proximity tool.
Because these features require a combination of Wi-Fi and Bluetooth to work, you’re likely experiencing a problem in how each OS or both of them determine whether they’re close enough to each other. (Some Continuity features work with just Wi-Fi or even devices just signed into the same Apple ID/iCloud account.)