but can not receive from that Secondary MAC.
It is not quite clear what you mean by that.
1) If you mean that you can't add connection with the first Mac in SyncMate on the second Mac, then I would like to inform you that there is no need to establish connections on both Mac computers with each other.
It is enough to add connection on one Mac, allow this connection on the second Mac and data will be mutually updated on both Macs.
2) If you mean that information from the second Mac is not transferred to the first Mac when you sync calendars, then please, provide us with the SyncMate Activity log during this sync.