Looking at the directory structure of this add-on, you will probably need to upload the files manually.
There's no predictable structure to this add-on ZIP file so it fails to place the files in the correct place.
The directory structure is like this:
PowerDigital > Unanswered > ~Files~
The directory structure for most XenForo add-ons is like this:
upload > library > PowerDigital > Unanswered > ~Files~
My Installer add-on doesn't necessarily insist on the above structure, but it is preferred.