I have recently paired a sonoff zig bee switch to the I host unit. I can’t get it to show up in the eWeLink app. Conversely the I host won’t sync the signee hub sub devices
You will never be able to do that. The only way to synchronize devices is from app to iHost, and this procedure is available for WiFi devices and more not for all of them, at least for now. That’s how iHost was developed.