Offline is a common status which can have a wide variety of causes, however if you have a lot of offline events occurring on the IQ Panel 2, the problem is almost certainly the panel RF antenna.
The sensor antenna on the IQ Panel 2 is the thin white flexible antenna. It must be routed out the back of the panel and into the wall for proper reception. If it is left in the panel or pinched in the back plate it can affect signaling for non-PowerG sensors.