Hi @AnnaB like @Ryan_Miles I can see the APs in another customer's Dashboard organization (actually two Orgs), as if they were never unclaimed from those Orgs, however they were never online or in use. When you say they gave you the codes, do you mean the serial numbers, or maybe an order number and/or a license key? And you say you claimed these 7 APs and they did in fact populate into your Organization > Inventory?
If so, and you did not unclaim them yourself, nobody else would have been able to claim them, it would give the same error that the devices were "in use" because they're already claimed in your Org.
You'll probably have to open a case with Meraki Support and the partner/reseller you purchased the APs through. Meraki Support should be able to investigate the order history and if and how these APs were ever claimed into your Org and/or removed from your Org and how they ended up in another customer's Org.