Hello Gerry,
The reply from Inspired Acoustics that you quoted appears to be referring to a Hauptwerk v4-format version of the sample set, since there's no need for an end user to contact MDA (or to send MDA anything) for v5-format sample sets. For a v5-format sample set IA should have provided you with an activation code (that you'd need to redeem via 'Licenses | Redeem Activation Code' in iLok License Manager).
I've also checked in PACE's system and I can see that the PAB licence that your account currently has is for the older (non-PAB3) version of the PAB.
Hence presumably IA mistakenly sent you the Hauptwerk v4-format version of the PAB3. If so, please contact IA to ask them to provide the v5-format version of the sample set (and an activation code) for it instead.