Can not import Apps purchased on another machine (Same iTunes Account)

Question

I was in the process of cleaning up my iTunes libraries and coping files between my two Macs and discovered that I can no longer import the .ipa file from one iTunes Library to the other Mac. When I try to import into iTunes, I get the error message saying: "The application could not be added to your iTunes library because it is not a valid application." With previous versions of iTunes, I have been able to copy apps between Macs. Both machines have up to date software and the same iTunes account. Both machines are authorized and work fine independently. Does anybody know of a new method of adding an iPhone/iPad application to your iTunes Library? Thanks.

Answer 1

All purchases should be available.  Are you sure they were purchased under the same ID?
It has always been very basic to always maintain a backup copy of your computer.
You should ALWAYS have a backup copy of your purchases.
When you bought records, you kept the records, just as you should keep the songs you downloaded.  If you throw them away with your ipod, then they are gone, just as if you threw away a record with the record player.
You can transfer itunes purchases from an ipod:  File>Transfer Purchases
It is 100% your fault if you fail to maintain a backup copy of your music.
You will never be happy with any digital product if you fail to do the basics.