I download an add-on, and the install is just unzipping into the “Applications” subdirectory of the Mathematica base directory. However, I try to copy my application into the “Applications” without any add-ons in the “Document center”. why?
Which add-on? Which verison of Mathematica?
If your add-on isn’t up-to-date, that might explain the issue.
If the add-on is made by Wolfram Research, contact Wolfram Technical Support at (support@wolfram.com).
I have a problem with the installation http://products.wolframalpha.com/referenceapps/stars.html
That is a different problem and not related to the one in this thread.
If you are having trouble installing something from the Apple app store, I would contact tech support for your device.
‘the “Applications” subdirectory of the Mathematica base directory’ is a standard location for add-ons. That directory is included in the default list of directories to look in for add-ons (the “$Path” variable).
I don’t understand your second sentence,
'I try to copy my application into the “Applications” without any add-ons in the “Document center”. ’