@Marquardt 

I tried that with the first one, then ordered a new one and have the same prob

I am also have this same problem.  Over the past few weeks I've installed 10 Wi-Fi enabled TP-Link switches, 2 of which as KS240s.  1 of he 2 KS240s began to exhibit this problem last night, i.e. both the fan & light LED is solid red.  This is not a problem with my Wi-Fi or my Internet connection.  I have yet to reset the KS240 using the reset button that is currently unrechable behind the switch cover I have installed on the KS240.  After reading these posts on this forum & seeing everyone else is having this exact same problem its clear to me that this is some problem specific to the KS240 product.  I've also just filled out the 'KS240 LED Feedback and Troubleshooting' referred to i this forum.  I'm now awaiting TP-Link to respond with a remedy to this problem with their product.

Sometime later 5/8/2024...  I power reset it at the circuit breaker, and not the reset button on the KS240 that is inaccessible behind the switch cover I have installed.  After power resetting it the LEDs changed to flashing red, and no longer a steady red that they were before power resetting it.  After power resetting it I had to delete from the Kasa app, followed by pressing & holding 1 of the fan/light buttons for 5+ seconds which apparently resets the KS240 to a factory default state.  I then added back back into the Kasa app.  So far its working again.

On 5/11/2024 it happened again, same as last time.  Both the fan LED & light LED were solid red.  The KS-240 disconnected itself from my Wi-Fi.  I reset it by the circuit breaker and not by the reset button on the KS240, which is inaccessible due to the switch cover I have installed.  The same 2 LEDs on the KS240 are now flashing, alternating between white & red.  I then have to delete it from the Kasa app because the KS240 appears to be in a factory default state (the only thing I have done at this point is turn the circuit break off for 2+ minutes, and turn it back on).  After deleting it from Kasa app.  I add it back as a 'new' KS240 switch.  At this point everything is working again, as it should... for now.  I'm still waiting for someone at TP-Link to respond to this discussion with a solution to this?  Both of my KS240s are less than 30 days old.  One of them has worked flawlessly, and other one is having this continuous problem.  Is TP-Link working on a solution to this???  Please advise!

  @Aravot I rebooted my network, and all three KS240's went solid red when swiched off (white with red border when on).  I've had them go red once before, but it's the first time I've seen cause/effect.  The router is Deco 6E (X75*?).

Is there any update on this?  Its getting annoying to have to constantly reset them.  Today just one went red on me.  I'm dissapointed in the product, having expected better as the 30 some odd other Kasa switches I have work perfectly.

  @Pop060955 I am an end users you should tag @Riley_S