Thanks, this was the problem. I think I was on the verge of realizing this myself - I had already noticed when I leave home only with my Android, the tag that I have in my car has no problem syncing…
On another note, as I asked earlier, is it (yet) be possible to get the synced data forwarded to my own DB via the data forwarding to URL feature on Android when syncing with tag? This would be really helpful as I don’t have the Ruuvi Gateway.