I'm having this problem with "Local Only" on one of my switches.  Just put 2 of them in about 3 months ago.  No problem.  Now there is.  And all the complaints I read here are over a year old.  So what do I do now?  Looks like you haven't fixed the problem yet.

@Carl So where's the answer?  It's been over a year!  Mine is an HS200.  And now it's gone to "Local Only" about 3 months after I installed it and another one (the other one is fine).  What's the deal?

@HappyInWA 

I ended up adding each devices' MAC address to my router's DHCP server's list of reserved addresses so they each have thier own assigned IP permanently.  Then I reset each one individually and added them back to the network.  This allowed them to clear thier local cache, but when rejoining the network (because the router was using the MAC address to assign an IP) each was given a static IP.  That resolved the issue for me.  Took time since I have about a dozen devices, but I've had zero issues since I did that a year+ ago.

@HappyInWA 

The deal is to accept your loss and move on. This only happened with older versions of the HS sockets for me and only one was actually thrown in to the bin. The other problematic ones started working fine when I replaced our mesh system with a Netgear Orbi RBK50 mesh network. 
 

Whichever way you look at it, Tp-Link are playing the quiet game as they know all too well that it's something to do with what they created and they don't want to take responsibility. Whether this means they are an irresponsible company that you don't want to deal with any more is for you decide. Personally I'm keeping what I've got until it dies then I'll consider all my options rather than spending any more money with them without question. 

@Stevieruss 

I disagree about accepting it as a loss.  If you look at my explanation above for a fix, most that have done this have eliminated the issue.  I do think tp-link erred in the execution...since one must link the MAC to a static IP, the issue seems to be in the way TP-Link handles comm with their servers through a private network that uses NAT.  But again, it's an easy enough fix, albeit a manual one, once it's done, it's done, and doesn't need to be done again, unless one buys a new router...but even then, copying the routing table to a new router is fairly simple and would prevent the need to redo a manual setup process again (assuming you keep the same network ip schema and network/ssid name and passcode).

@Carl 

I am beyond frustrated with this situation. 
 

I just bought 13 TP-Link smart switches and I PLANNED on buying 10-15 more to have my entire house on them but this is absolutely going to keep me from doing that. 
 

if the older model has an issue that causing DNS error than why sell them? 
 

I bought 2 of the 3 packs thinking, great, what a good deal. 
 

and now after $200 for switches, new plate covers and about 2-4 hours worth of time I have switches that do not work with Alexa. 
 

I have been a customer for years between carrying some of your products in my retail stores, to the Deco mesh wifi and various smart plugs I now have a decision to make. 
 

it sounds like TP isn't willing to step up to the plate to repay any of us for this HUGE/MAJOR/UNBELIEVABLY terrible situation. 

sure, we can go into our routers and do this and do that but the reality is we shouldn't have to. This product should not be sold if it requires complex knowledge of networking. 

FYI going into my router app and toggling the internet off and then on for the device that is showing local only cleared the problem. Literally just toggled off. Waited maybe two seconds. Toggled back on. All was good again. 

I was showing blanks for time zone and device time.

My device did eventually switch to local only again but toggling its internet via my router fixed it again. So it isn't a perfect solution but it is a work around, especially if you are not at home and need to be able to control something immediately.