Can't get Office 2013 to activate after reinstalling

Question

So recently I had to reinstall office on 2 PCs for a nonprofit I volunteer with. I always just kept backups of any software installers as ISOs so in times like this it’s a simple reinstall then update. Well, it’s been a long time since I had to do this and for one reason or another Office will not activate using the MAK Key for it. It just says this is not a Microsoft Office 2013 product key. So, I click on get help and that takes me to a 404 not found support page. So, I figured ok I’ll go to the Microsoft volume licensing page, log in check for the MAK Key, and make sure it's the right version of office. I guess at some point that got rolled into 365. So, I try to log into that with the Microsoft account the key was obtained on only to get "(email) isn’t in our system. Make sure you typed it correctly". So, I am kind of stuck at this point. This version of office along with widows was bought years ago through TechSoup so while I could advise the nonprofit to do that again I am trying to save them some money as they are perfectly happy with this old version and it’s still up and running just fine on 2 of the other PCs they have. Any help would be appreciated.