At least under older operating systems, Air Drop comes up as OFF. You have to turn on both Bluetooth and WiFi — and then select Contacts or All. You may know that already, but in case not, thought I’d mention it.
If AD is set to Contacts Only, you need to create an address on the iPhone that matches your Mac's name (IIRC). (Or, vice-versa, if you are ADing the other direction.).)
Easiest trouble-shooting is to set all devices to Everyone. Can you Air Drop between your Macs?
Perhaps your new Macs don't have your iPhone in their contacts list. Should work with Everyone, though, unless all that's been changed under Big Sur.