vanagsgMy suspicion is around the number of the devices and the location.
At your work everything was OK but there you had only two devices, like I did when I went at my friend's house.
Another thing that happened some time ago, I had gone at my other house in another city. When I was there I had tried some things, made a hotspot with my iPhone and mac was connected through it then I restore the network settings on my iPhone and Airdrop was working between iPhone and MAC! When I tried my iPad, Airdrop was not working not even between the iPad and the iPhone and it has always worked among these two.
I don't recall what I did then but I managed to have airdrop working between my Mac and my iPad. Guess what? Airdrop was not working between my iPhone and the other two devices afterwards. It's like there was a limit of two.
Unless we find a pattern for this problem this forum will continue for ever.
When I say pattern I mean that from state A ( airdrop not working ) we do some changes ( delete a file for example ) and we reach at state B where Airdrop is working. Now if we undo these changes ( restore the file ) we should return to state A where Airdrop is not working.
Then verify that if we to state B again Airdrop will work. If then we analyze the factors that change we can find what causes the problem and have a solution that will work for everyone!
I feel that changing the contact info is not the source of the problem, it's just triggers a series of events which repair the problem. When I went to my friend's house I didn't changed anything, no contacts, didn't deleted files. It just worked! The only thing which did changed was the location of the devices on the iCloud which probably triggered some events and made the Airdrop work again. When I returned home I tested again with there different routers (two land line and one 3G) No success.
What I am trying to do next is take my iPad to my friend's house log in, ( it's location will change )then turn it off and when I get home test if Airdrop is working among iPhone and Mac.