I did some more checking - at the time of the upgrade I also set up Safari iCloud tabs for the first time. For some reason - maybe because my iMac is so old, I think the tabs disappeared.
Anyhow, I turned off iCloud Safari on the iPad (data from other devices was not showing anyway) then tried. Tabs remain, even after shutdown. I re-enabled iCloud Safari. It kept working OK. But still no data from the other device (iPhone 6)