I just purchased and received 2 new HS220 Dimmer Switches from Amazon seller EverythingDeals. Both switches fail to show power on the front when connected, the corresponding circuit breaker is on, and power is being delivered. The switch is to replace a standard single pole toggle switch. The electric box provides all 4 leads: load, live, neutral and ground. I connected all 4 properly, being sure that the load and live wires each go to the respective load and live terminals on the switch and the ground and neutral wires each go to ground and neutral wires on the switch, respectively. When power is being delivered, the switch doesn't show power (no green or orange light on the front). I measured with a voltmeter across the wired load terminal and the ground wire, and the load terminal and the neutral wire, and both show 120VAC, so I know for certain there is power. I verified that all 4 leads are properly connected, including tugging on the wires to ensure the connections are secure. Neither switch works! I have a lot of experience doing electrical wiring, so this isn't a matter of naivety.

I find it hard to believe that both are faulty, but perhaps both are from a faulty manufacturing run. Their closely numbered serial numbers support this possibility. It may also be the case that the Amazon Seller, EverythingDeals, sent me 2 previously returned, faulty switches, declaring them as new. My basis is: both boxes have a sticker on the bottom covering the UPC code on the box, each with a bar code "X003YVQZ5R" that is different from the partially visible UPC Code on the box and also state "New".

These switches are model HS220 and hardware version 3 (deduced from the IC number on the back side of the switches: 26583-HS220V3) and the box and switch each also show "Ver 3.6" and ""US/3.6", and have serial numbers Y22C0H1004087 and Y22C0H1004083.

I also read the post here, which unfortunately doesn't conclude with the outcome (an ongoing fundamental problem with forums, where you have to hunt and read ad-nauseam until you get the information you need, if ever ... life was so much better when there was actually an educated technical assistant available by phone without a ridiculous waiting time). I've definitely met the requirements in this other post and in my case, actually have all 4 wires properly connected. Here's an excerpt from "expert" Solla-topee in that post:

Correctly wiring HS220 requires at least 3 lines in your electrical box: 
 1*Live wire, 1* Load wire, 1* Neutral wire, 1*Ground Wire (optional)
(NOTE: If  No Neutral Wire is present, HS220  can Not be installed   )

•        WHITE wire on switch to NEUTRAL wire.
•        GREEN wire on switch to green/bare copper GROUND wire.
•       Two Screws on the right side of the switch:
        LIVE screw must be connected to LIVE wire 
         LOAD screw must be connected to LOAD wire

If still the same issue, the switch could be defective, can you help provide the Hardware version & SN number as well as the proof of purchase.

I won't be providing proof of purchase here as Amazon fortunately provides 30 day returns. If I don't get a useful reply soon in this forum, I'll purchase a different brand. I'm not married to Kasa or TPLink, even though I have several of there devices that actually work.