airtag not showing location when my phone switched off - other iDevices nearby.

Wifes phone location services are on - as is location sharing with family.

I've also set one of the airtags to lost mode in case that is requried to get it to transmit location through other devices..

Even more weird.

We share our locations with each other. My wife's find my reports last contact with my phone at 14:36 today - my find my on my iMac is still saying 00:12, but on my Macbook Air, is showing (like my wife's) 14:36

Surely find my just looks up location on a server - doesn't it?

Some more testing. These tags don't seem to be able to report location except when in range of my phone:

Two tests. I moved one to the bottom of the garden out of range of my phone, but about 5ft from a walkway along a busyish road. In about 6 hours with people walking past, no location registered. (I'm guessing some must have had iPhones with them)

My wife is now away from the home with her keys airtagged (but linked to my account). She has her phone with her, on and bluetooth on, find my on, and location sharing on (I can't find a specific relay setting to turn off or on her phone). So far it has been about 25 minutes since she left.

The airtag has not yet updated its location.

I can see her phone location, so location services and sharing is working.

Does the relay feature need a specific IOS version? EG 15 (her phone not updated to 15 yet, but does have 14.7)

Update - the airtag loaction is now shown now she has reached a destination.

However, only on my phone. On my mac the same airtag is still saying "last seen 10th October...."

Find my does seem to behave strangely.