@MarkNI 

I had to switch my broadband off (I was experimenting with Bluetooth performance near my router).  I noticed all 3 of my TP plugs went red (as expected). I turned the broadband on again about 10 mins later and then I was in the attic for 1/2 hour.  I came down and remembered I must reset the plugs, but I found all 3 were green.  So my conclusion here is that they do periodically try to reconnect or reset themselves when they lose connection, but the problem/bug (in my case anyway) seems to be that they are sometimes locking up / crashing either in the disconnected state, or during the process of handshaking/reconnecting.  This info won't really help any fellow sufferers, but I thought I might as well share in case someone from TP is listening....

@MarkNI I have seen this also.  The problem is sometimes they do and sometimes they don't! To many frozen devices in the last year to stay with the tplink devices.  I have slowly switched them to Sonoff devices with custom firmware (Tasmota) and I now have 10 working with zero issues.  

@DRBG,

It's not in app's Settings; it's in the device's settings.

Select the device from the Devices page. Then press the gear (settings) icon in the upper right corner. Then select Device Info.

This is crazy.

I have had a HS105 for almost 2 years and never had an issue - works all the time - every time. I bought a 2 pack of HS103s and they kept losing connecting. I figured that might be why they were so cheap.

I returned them and bought another HS105 and the same deal....this thing keeps dropping the wifi after like 1 hour or 2. If I didnt have a HS105 that works flawlessly for so long I would think this whole line is junk.

Im on the latest firmware and all that....anyone have a resolution to this?

@pingywon These units mostly work, but are defective.  I have lots of them and most stay up, but some don't.  Part of the problem seems to be the strength of the wifi signal... too weak and they have problems.  They don't seem to have error correction in the protocol.  Once they go off line, that's it until you power cycle them.  A repeater makes things worse, so if your wifi is using a repeater, try to eliminate it.  The only way I could get one to work was remove the repeater and go with the weaker signal.  Sometimes power cycling the router will get them to come back, sometimes not. 

The HS-103 does something unusual with the signal and can knock an Asus routher offline.  I contacted Asus, but they said since I bought it at Best Buy, Best Buy provided support.  I contacted Best Buy and they wanted $50 to look a the defect in the router.  I don't want to pay to debug their hardware defects, so I'm not paying.  I just won't use their equipment.  Even so, HS-103 behaves differently from HS-105 and other TP-Link devices.  It's probably violating something in the standard, but most routers are forgiving.  The Asus assumes devices are compliant and crashes the wifi when they're not.  Neither company cares about this problem, even though it is incredibly repeatable. 

If you can switch to a different plug, I would.  This seems not to be TP-Link's primary business and they just don't care that it doesn't work.  You can see from the length of this thread the problem has been around for years and they haven't addressed it.  A firmware upgrade should be all that is necessary. 

@RickA 

I switch the the sonoff brand (different types) and used the custom Tasmota Flash.  No issues.  Works as it should.-

@Carl - was this ever resolved? Mine lose connection once every few weeks or months. -55 & -34 dbm. They connect right away when I unplug and plug back in. Both are HS105 / hardware 1.0 / fw 1.5.6.

It seems like there should be something where it tries to reboot its WiFi card, instead it just fails and I have to reconnect them. I control them a lot via the Kasa app so it irks me a little when they aren't connected and I see them just flashing blue in the sockets, clearly in view with router. No issues with any other devices on the network and these work great 99% of the time.

@SDG-88 I resolved it by switching to sonoff devices for anything critical.