Invalid signature when trying to install Photoshop CC extension using the Adobe Extension Manager CC and default installed Photoshop CC extensions won't load

Question

I have a Creative Cloud subscription for Photoshop CC. All Creative Clouds products are updated to the latest versions. When I tried to install Tony Kuyper's TKActionv3 Photoshop extension using the Adobe Extension Manager CC on my PC desktop, I received an error message that the extension contained an invalid signature and wouldn't be installed. I had previously installed the extension on my laptop without any problems. At the same time, I also noticed the default installed Photoshop CC extensions (e.g., Adobe Exchange, Kuler, Mini Bridge, Behance) could not be loaded using the Windows/Extension command. I receive an error message that the command could not be completed because the extension could not be loaded. After contacting Tony Kuyper, he suggested that I try the steps mentioned in the following weblink: https://forums.adobe.com/message/6029768. The steps basically consist of uninstalling and reinstalling all the Creative Cloud apps associated with Photoshop CC. I tried the steps multiple times, but I am still having the same problems. I can find the default installed Photoshop CC extensions on my machine, so I don't know why they can't be loaded.
Thanks for your assistance,
Mark Curtis

Answer 1

Hi Mark
You say everything is up to date?  And you have tried reinstalling all the CC apps?  Is Windows also fully up to date?  Hmmm...  That could be tricky.
What version of Windows are you using?  Have a look in Task Manager > Processes and see if 'CEPServiceManager.exe *32' is listed as running?
If not, I don't know where it would be installed from, and we'd need someone like Chris Cox to join the thread to tell us, but my guess is that it would install along with the CC Desktop Application Manager.  Windows 8.1 can be problematic, and a bit fussy about the order of things, and it is definitely worth adopting best practice when installing your CC apps.  That means restarting your computer, and right clicking the Desktop Application manager and running as Administrator.
How many CC apps are you running?  If just Photoshop, Bridge, Expansion manager etc. then - and I hate to say this - perhaps have another go at reinstalling, but run the Cleaning tool after uninstalling.
Use the CC Cleaner Tool to solve installation problems | CC, CS3-CS6
Try some other Extensions before the Tony Kuyper's TKActionv3.  GuideGuide is a favourite of mine, as well as Dmonzon tools, and maybe Russell Brown's Flypaper Textures. 
I have to say that I have had problems with the CC Extension Manager a while back, but simply reinstalling just the Extension Manager fixed it.  Perhaps CEPServiceManager.exe *32 installs with Extension Manager?  Heck, maybe start with just trying that before reinstalling all your CC apps.
If you are still stuck, I'd risk sending Chris Cox a PM, but not until you triple check that your video card driver is up to date from the card maker's website.
Good luck, and be sure to let us know how you get on.