@LeVeau,

To be clear: You are having problems with the P125M's Matter Connection to Alexa?

A few things that I would recommend trying:

1. Link Your Tapo Account to Alexa to see if Alexa can control the device via the cloud connection.
2. Ensure that your device is up-to-date through the Tapo App.
3. Try Creating a Routing or Group and setting the devices to turn on via a different command.
4. Try changing the type of device in the Alexa app from plug to light, or from light to plug. If your device included "light" in the name, it may have been automatically changed to light and may need to be changed back.

From looking around other forums, this seems to be a behavior that was first seen in 2020 with a variety of brand's devices - with the main recommendation from the Amazon team being to reset and re-add the devices. Unfortunately, this was before Matter was released, so it is likely a platform bug on Alexa's part. 

Since the device was reset, you may make sure that the device was completely deleted from the Alexa app, and you may consider using a completely different name when setting up the device again. Settings may be saved in their cloud and causing the problem.

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As a side warning, based on the number of controllers you have tried, you may be approaching the maximum number of controllers supported by the plug. It has been a long while, but I believe that they support 5 different controllers (with Tapo consuming one, and Homekit actually consuming two).

  @LeVeau,

First, there is a difference between linking your account and using the matter setup:

Linking your Tapo Account to Alexa allows for Cloud Control of Devices through the TP-Link Cloud,

Using the Matter Setup Code and Process found in the Alexa App allows Alexa to control the devices locally via a Hub, without the help of TP-Link at all.

You may be best suited to ask the Alexa support team if it is an Alexa group, but are all the devices in the TV lights group the same type of device? If one is an actual light bulb or strip, try removing it and trying again with only plugs. Also, while it may work individually, you may still try changing the name, as it may work differently when being calculated in the backend and will refresh the settings.

I believe that I added that HomeKit note simply because of how the different platforms had implemented matter, but it is actually the reverse.

Essentially, once a matter device is added to a controller/platform, you cannot just reset the device to add it to another platform - otherwise it will delete the configuration for the first. Most, but not all, Matter apps have an added option to add the device to another platform via a pairing code at this point. If going through the matter setup process, you would basically hit a wall where you would not be able to find a pairing code if you added the device to a platform that did not have the feature and wanted to add it to another matter controller.

I would highly recommend going through the actual matter setup process for Alexa and Homekit, as your commands are sent directly from Hub to Device and you will likely have a much more stable experience. Currently, you are still using a normal Wi-Fi connection and are not taking full advantage of the matter compatibility - but keep in mind that you need a compatible matter hub for setup.  You can either use the included QR codes or find the QR in the Tapo app, as shown below:

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From a Soon-To-Be Released FAQ:
Please set up your Matter-enabled devices to Tapo/Kasa first, then you can refer to the steps below to find the electronic Matter setup code in the Tapo/Kasa App.

Tap your Matter device finished setup in Tapo -> Tap the gear icon on the top right corner to enter Device Settings page -> Tap Device Info -> Tap Matter Setup Code -> Then you could find the electronic Matter setup code, it's suggested to save it to the album of your phone for use in other apps.

  @LeVeau,

If you want that matter/local connection across your devices/hubs, then yes. The Alexa functionality should have no problems controlling the device via the cloud integration, but you may personally have a better and more stable experience with Matter control.

I do not believe that HomeKit has added the pairing code functionality yet. So you you would likely want to use the Alexa setup method first, and then add the device via the pairing code to HomeKit

Essentially, you would be looking at using either the matter code from above, or the matter code in Alexa. This would allow both Alexa and Homekit to control the device locally / via matter:  https://www.amazon.com/gp/help/customer/display.html?nodeId=T6iLWTtbZygaBJnQhg

You may also consider disconnecting and reconnecting your Tapo account from Alexa to see if this will refresh the settings for the groups and devices. The devices like automatically reappeared due to the cloud integration set between Alexa and HomeKit or between Alexa and Tapo.