Regarding this problem, it seems most likely a DNS resolution issue. The default DNS servers assigned by your home router cannot resolve the TP-Link cloud DNS server successfully.

We recommend to change the DNS server on your router as 8.8.8.8 for a try. You can google "how to change DNS on XXX router" if you don't know how to do that.

In addition, please kindly check if you have restricted the internet access for this plug as well. Thanks.

That’s a bit extreme for a 15 buck smart plug! Changing the router DNS server for what is probably the cheapest bit of equipment on my Network is not an option. I have two plugs, first one absolutely fine, New one has this problem. Identical models. 

That is an extreme solution indeed. It seems like a firmware error on your end here, is there another option to resolve this issue? 

Otherwise I have no choice but returning both plugs. They are completely useless if remote control is impossible - I need a workable solution for this, changing DNS server is not. 

Can you look at my issue again please?

Do you have a computer connected to your Wi-Fi network?

If yes, please try to make a DNS resolution on your computer for a check at first.

Let's take Windows PC as an example. 

Tap the Start menu and type 'command prompt' in the search box. Then open the Command Prompt application.

Then please type in 'nslookup devs-gw.tplinkcloud.com" and press Enter key to execute the command line. Check if it can give a result with IP addresses. 

If not, it seems that your DNS servers assigned by the ISP fail to resolve the TP-Link cloud website. 

Hi there

I just did what you suggested in command prompt, and I actually do get a result with multiple IP addresses. Does this mean the DNS server configuration is correct? 
The problem is still there unfortunately.

For people who had the same issue and are wondering about the solution - after communicating my MAC addresses to the TP Link support team the issue has been solved :).