Manifest.xml Installation Error
If you get the following error about invalid manifest.xml file for the Extension Manager:
There are a couple of things that can be done to fix this:
Option 1: Update your Adobe Extension Manager
You need to update the Adobe Extension Manager before you can go on.
Updates for all Extension Managers: www.adobe.com/exchange/em_updates/#em.
Option 2: Re-install your Adobe Extension Manager
If that does not work, please uninstall your Adobe Extension Manager, then download and install the correct version for your version of Photoshop:
Adobe Extension Manager CS6 for Adobe Photoshop CS6 (at the bottom of the page).
Adobe Extension Manager CC for Adobe Photoshop CC & CC2014 (at the top of the page).
EXTRA STEP: If re-installing Adobe Extension Manager did not work
Reboot your computer and try installing the panel via the correct Extension Manager again. It should work now.