I’ve had the same problem.  The funny part is that some of the bulbs that have dropped had timers on them that are still working.  I just cannot get to them to turn them on or off or set a different brightness level.  They don’t show up on Alexa or the kasa app.  

I've experienced exactly the same problem. Well, scratch that, mine "disappeared" but still show.

Despite making no changes to my network or to my TP-Link Kasa inventory, I no longer can use any of my devices.

The symptoms as as folllows:
 

• All devices showing on the list in the Kasa app; however, all are grayed out and cannot be controlled, edited, or checked for status.
• Unable to troubleshoot or fix the setup of any device. All just flash blue and occasionally are stuck in orange. But they are unresponsive.
• Cannot reset and add the device again. Just sits and spins on blue/orange.

I'm completely shocked as everything worked flawlessly for several months. This is really unexpected for TP-Link, which has always been a go-to for me.

I can only conclude the entire set of switches and lightbulbs is bricked in some way.

With no word from the company, I'm guessing they do not back the product.  Is it end-of-life?

I guess my experience with IoT will be a lot more shortlived than expected.

@Tova Same here - all devices are gone in the app, no switch is responding through smartthings or homeseer.

So it would appear that tp-link has no support.