Can't Expand Exchange Distribution Group from a replicated AD

[xxan0xx]

Ok... so I'm running into a wall fixing an issue in Active Directory / Exchange / Outlook. Basically the issue that I'm running into is the we have these Global Distribution Groups that used to expand from both domains and you could send inbetween them just fine and now if you try to send them inbetween domains it bounces, but only to distribution groups.

Here is an idea of what our infrastructure looks like.

Tier 1
Domain- enterprise.local
Domain Controller - Master-DC1: Holds FSMO roles, Schema Master role

Tier 2
Domain - site1.enterprise.local

Domain Controller -
Site1-DC1.site1.enterprise.local - Holds FSMO roles
Site1-DC2.site1.enterprise.local - Holds Global Catalog, Exchange Admin tools

Exchange Server-
Site1-mail1.site1.enterprise.local - Primary Exchange server for site 1


Tier 3
Domain - site2.enterprise.local

Domain Controller
Site2-DC1.site2.enterprise.local - Holds FSMO roles
Site2-mail1.site2.enterprise.local - Hold Global Catalog
Site2-mail2.site2.enterprise.local - Holds Global Catalog

Exchange Server-
Site2-mail1.site2.enterprise.local - Primary Exchange server for site 2
Site2-mail2.site2.enterprise.local - Replicated Exchange server for site 2


Basically I've ran into a wall and I'm not sure where to look because all the replication is taking place and there are no errors whatsoever so its looking like an Exchange permission Issue but I'm not sure where to start. I've been looking and looking for the answer to this but I'm just not having any luck.... any help would be much appreciated