@aroedl or TP Link make the right adjustments to your account. Then the KE100 will appear again.

This happened to me after contacting support about this issue.

And yes, TP Link is always aware about this issue.

  @aroedl 

Update:
In the first step I installed the KASA app and in the second the TAPO app (Vers. 3.2.808 - idea from reddit/aroedl / you?).
When installing TAPO, it shows that the KASA app will be included.
Now I have connection to my KE100 again.

Old versions of TAPO can be found at “apkmirror com”.

  @DLuebker 

Yep, that's me on Reddit.

If you update to the latest version, can you still see the KE100s?

  @aroedl  Hi aroedl,

I'm not testing the latest version for now. I'm glad it's working this way.

Never touch a running system.

  @DLuebker 

@Wayne-TP Can you please take care of this serious issue?

  @DLuebker Since Tapo 3.2.515 (first version with KE100 support) I deleted all my KE100 including Kasa KH100 Hub in the Kasa App. Because it is no longer needed.

After linking my Kasa account with my Tapo Account (same ID) in the Tapo App.

I've added all my KE100 (4) to my existing Tapo H100 Hub via Tapo App. This worked till version 3.2.808.

With version 3.2.974 all my previous added KE100 are still present in the Tapo App. And I'm able to configure and adjusting my valves. But since this version the option to add more KE100 was gone. 

Simply no option under add devices/ Kasa. 

This was the point for me to open an support case (ticket) by TP Link. They send me some Trial versions of the Tapo app for logging and creating support data.

TP Link found some clues and then makes some special adjustments to my account.

And a few days later the option for adding another KE100 appeared again in the Tapo App 3.2.974. No need for logging out or deleting/ reinstall the app. But my KE100 never completely disappeared in the Tapo App. This seems now the case (not for me) with 3.3.513 in conjunction with this "special" (internal) settings of your TP Link ID (Account).

And the option for adding and the KE100 themselfes are always present in the app, also after updating to latest version 3.3.513.

Yes. Since KE100 is working in 3.2.808 also without "special" account settings. This version takes no care about these settings. So maybe an new version (update) may fix this issue also without account setting adjustments again. Maybe it has something to do with updates in TP Links Data Security Guidelines and DMA (Digital Markets Act) here in Europe.

  @aroedl  You can still use the KE100 in the KASA app. It is a KASA device.

  @Pandalorian 

Why should I use two apps instead of one? It worked before. What about automations? Do you think that they work between both apps?

From what I've heard, the Kasa brand will be phased out in the future anyway.

  @Pandalorian Of course but I prefer one App - one Hub...

And KE100 support was officially implemented since version 3.2.515/ 3.2.808 and above in the Tapo App and should also be working in version 3.3.513.

Since no official announcement from TP Link related to removing KE100 support in Tapo app again.

  @aroedl Not always two apps, also two hubs. In Tapo app you can also add your KE100 to your Tapo H100 Hub (if present). Works flawlessly.

PS: On TP Link Matter Site (Germany) under upcoming products, is also an KE200 (Matter) listed.