I am running into the same problem/issue. I had purchased a copy of Office 2011 1-user license from Microsoft's website. They gave me a product code, which I used to activate the software on a Retina MacBook Pro last year. I did a completely wipe/reinstall of the system software, and sold that Retina MacBook Pro. Then, I used the same code to install and activate Office 2011 on an older 2007 iMac. I just purchased a new MacBook Pro, and was hoping to be able to install the software and activate it with the license code, since I deleted from the iMac and the iMac is packed away in storage now. It tells me "Activation was not successful because the maximum number of installations have been used"
Apparently...Microsoft's Office 2011 for Mac Activation system works like this...you are paying for a License key which will allow you to activate the software with Microsoft's online system on *two* different computers, but NO MORE than two. If you have used ANY activations of that code on the past on two different computers, all of your activations are USED UP and the system will not allow you to activate the software on a third different computer, even if the software is uninstalled or not present on the previous two computers.
THERE IS NO WAY TO DEACTIVATE OFFICE 2011 ONCE YOU HAVE ACTIVATED IT.
Once it has been activated on a computer, the activation for that computer is used up....you cannot "de-activate" and free-up the install for another separate machine. Microsoft will not allow it...
This is the frustration I am running into. I have already spent over $500 on Microsoft Office software and currently only running it on two computers. Ridiculous. And I am going to have to buy another license if I want to install it on my new MacBook Pro because all of my other activations are used up on separate machines, which I do not even own anymore - Microsoft records a machine code with your product key for each machine you activate, and has a max number of unique entries allowed per product license, usually 2, 3, or 5.