So first things first,
Are you SURE both devices are on your Smartthings Zigbee network. You can figure this out by doing the scan in XCTU using your Xstick and scanning the network and comparing the Zigbee ID’s and the Device Network ID’s you find listed in your IDE device list.
This was explained and suggested earlier in this thread that you look and compare to make sure both devices are indeed on the smartthings network.
Here is a scan of my network
The item in green is one of my Xbee radios plugged into my PC, the item in blue is another I have set out by my shed. If you look at the numbers in the white box for each item on the mesh you can figure out who is who using your IDE device list.
Here is a snip from my device list of the 2 Xbee radios
Notice that the long string of numbers in the white box of the device match to the Zigbee ID on my device list. The short string of numbers under the white box match the Device Network ID in my IDE device list.
So I know those 2 devices are indeed my 2 Xbee radios. So I know for sure that the Xbee radio is talking to everything else on the network.
Next Item, are you sure your devices in the shed have joined smarthings network? Did you do it in the house and then move them to the shed? Do they work again when you bring them into the house? If ALL that is true then they should not be the problem.
Next Item, as has been said several times now. Just because your plug in extender radio can reach your remote devices (in theory, since its a stronger radio) does not mean your battery powered sensors can reach back to it across the 30+ feet of yard, through building materials ect…
The standard practice (as has been said) is to put a main powered device with a stronger radio CLOSE to the battery powered devices. LIKE IN THE SHED. Then this device can link to another main device and possibly span the distance.
I understand you do not have power in the shed so that really isn’t an option for you.
So if you scan your network and BOTH devices (Xstick and plug in module) are indeed there. Then you pulled the battery from the sensors and reinserted it (hoping they will forget their preferred repeater, and join a new one.), Possibly even turn off your HUB completely for say 20 minutes ( force devices to rebuild mesh network). If after ALL that you still can not see your devices in the shed or get your devices in the shed to join smartthings network. Then your battery powered devices in the shed 30+ feet away can not reach your plug in module next to your house.
That’s just how it is and if this is VERY important to you to have these devices on smartthings then you’ll have to find a way to get power to the shed or power to a repeater that is close to the shed and can still connect to another repeater that is close to the hub.