I'm on an Archer C3200 router, which is a TP-Link product.

@NikD63 Hopefully someone from tplink is monitoring this forum.

@bschatzow I'm using a BT Smart Hub AC 2600 - fairly common here in the UK.  I also had a TP-Link 24-Port gigabit switch, but I've since taken it out of the equation with no improvement.  I think it's a bit silly for them to blame the router if no other devices are having issues with it.  If everything else can cope with it, why can't their plugs?  And why can't they automatically POR as a temporary fix without us having to do it to manually recover them...

@bschatzow, Carl from tplink was monitoring this thread back when I was still having issues. I don't know if he still is; the last post from him I see is from June 2019.

@NikD63 I linked this thread to my support emails.  They have not responded to this either.

The same problem.... after almost one year with those devices... managed by Alexa App and configured by Kassa App, I really hate them because all the time that there are a WiFi lost I have to unplug and plug foe reconnections.... I did try to firmware upgrade and nothing work... if the problem doesn't solve ... I will change to other brand

I am having this exact issue, and have been, every time our router craps out and reboots, the Kasa HS100 does not reconnect, it just sits there with a red LED until I power cycle it, quite frustrating.

I finally gave up.  I trashed all my TP-Link Kasa plugs and bought Wyse plugs.  I haven't had a reconnect problem since - about a month.  With the TP-Link plugs I would have had to unplug them a dozen times in a month.

The Wyse plugs do not have a native sunrise/sunset option but IFTTT works great.  Another bit*h I had with TP-Link is no offset option for the sunrise/sunset but the IFTTT trigger allows me to select my location on a map.  I just select a location a little east or west of me and I can fine-tune the sunrise/sunset function.  Technically you could do that with TP-Link but it's much more cumbersome as you have to play with Lat/Long trial and error.

I gave up on Kasa as well.  I've spent way too much money on these plugs.  I've used them in 3 different network configurations, even replacing one expensive router with another to see if that was the issue.  Nope.  I replaced them with Gosund plugs and have had zero issues.  I really wanted Kasa to work, particularly because I liked the interface with the little app.  But after ruling out everything else, I've determined the plugs were in fact the issue.

I've purchased a lot of TP-link hardware in the past but the manufacturer's inability or carelessness has made me rethink any future purchases.  I'm going to find new suppliers.