I ended up finding the answer myself. Apparently, TP-Link neglected to make this clear on this HS220, but this only works with a single light bulb. I came across Amazon reviews sharing this after they worked with TP-Link support, and sure enough, when I unscrewed all light bulbs but one, it worked perfectly. Of course, this still makes this switch useless to me... I wish TP-Link was more forthcoming about such a huge limitation on this device. I don't know if I can return this switch to my local store because I didn't keep the box. Not happy with TP-Link for the first time :(

@Solla-topee With all due respect, telling a consumer to look for or change a compatible light fixture is not an appropriate solution or suggestion. TP-Link needs to be transparent about this product's limitations and print them on the product box and online product pages on all sales pages across retailers. A simple search will show you that there are a number of people who were extremely inconvenienced by this issue. I put my HS200 back in. I am not wasting any more of my time or money for this junk.

@tswielder Ok, if you have one incompatible bulb, switch can work, but if you have two at the same time, it could not work properly. It is what everybody is trying to tell you.
On another side I would be happy if kasa switches were more compatible with wider variety of bulbs, but we have what we have. For the price there is no competition for now.
Tuay clone switches sold in NA are not better at all and they are just pennies cheaper.  If you need quality, than go Philips for 3 times the price.