When Adobe configures mid-sourcing/domain delegation then they would have configured your DKIM keys if not your mid sourcing is not properly commissioned. Ask neolane support to fix it for you.
As part of domain delegation, adobe deliverability tea should configure below for your account
Implementation of an SPF record (Soft fail) allowing email signatures
Implementation of a DKIM record (Key in 1024b) allowing email signatures
Implementation of a DMARC record allowing email signatures
There is no action item on your behalf for DKIM key as this is a part of header information added by mid sourcing to your delivery and the domain you are using as sender domain i.e. customername.com etc