The default security setting for AddIns is to load AddIns without restrictions. Your organization may have set this setting too high which stops the AddIns from running or, for some reason, the out-of-the-box install set the security setting too high as shown below.
The Add-In Manager shows only ESRI AddIns are allowed and unusually the other options are disabled.
You can solve this by resetting the registry setting as discussed in this article to zero. This will require administrative privileges.