Hmm it is possible there is a software bug but if neither got updated then i couldn't say for sure.
Did you try turning on/off Wi-Fi and Bluetooth on both the iPhone and Mac, and ensure they are connected to the same network?
Also, are both devices signed into the same iCloud account? Perhaps you can try re-signing into the accounts? I have an iMac that is signed into my Apple ID but not iCloud and AirDrop works intermittently at best with my other signed-in devices.