I guess you have updated you Photoshop. The author has specified that supported Photoshop version is [13.0, 13.0]. It means that if your Photoshop version is 13.1.x.x or something similar, Photoshop will not load this extension. The Photoshop CS6 version in my machine is 13.0. I installed this extension and it does show up in "Window/Extensions" menu.
I think the author of this extension should specify the supported Photoshop version as [13.0, 14.0) so that all Photoshop CS6 versions will load it.
Actually, no, I haven't. My Photoshop is also 13.0. Apparently, there are a number of people that have had this problem. The recommendation I got was to download the configurator and make my own panel. Which I did. Unfortunately, I can't find a way to put the foreground and background color chips on the panel I created, and since I use those extensively, it's not very useful as it is.
I still think the root cause is that your Photoshop version doesn't meet the requirement of this extension. Note that if your Photoshop version is 18.104.22.168, it doesn't fall in [13.0, 13.0] either.
There is a workaround so you can use this panel. You can change the extension file extension from ".zxp" to ".zip", then unzip it, copy "content" folder to "<PhotoshopInstallFolder>\Plug-ins", restart Photoshop. You will find "Configurator-Panel" under "Window/Extensions" menu. This is what you want, although its name is not "All Tools CS6". In this way Photoshop will use the swf file name in "content" folder as panel name. If you doesn't like this name, please rename all related file names.
The best solution is still to ask the author to change the version range in this extension.
This worked like a charm. I renamed "content" to the name I wanted and now that name shows up. You also need to load it into both versions of PSCS6, 64 bit and X86.