How to create Exchange dynamic distribution list using multivalue extension custom attribute

Question

I am trying to create a dynamic distribution list using an ExtensionCustomAttribute.  I am in hybrid mode with Exchange 2013.  The syntax I have is this: 
New-DynamicDistributionGroup -Name "DG_NH" -RecipientFilter {(ExtensionCustomAttribute2 -eq 'NH')} 
This works correctly on-prem.  But hosted always results in an empty list.  I can see in dirsync the attribute is in the hosted environment, but for whatever reason, the distribution group gets created but always come up null.
If I create a group looking at the single valued attributes, such as CustomAttribute6 -eq 'Y', it works correctly on-prem and hosted.  
If anyone has any suggestions I would appreciate it.

Answer 1

I don't think I provided enough information about the problem.  Let me add some and see if it makes sense.
I have an Exchange 2013 on-premise configured in hybrid mode with Office365.  For testing purposes, I have 2 users, Joe and Steve, one with the mailbox on-prem, and the other with the mailbox in the cloud.  Each of them has CustomAttribute6 = 'Y'
and ExtensionCustomAttribute2 = 'NH'. Dirsync shows these users and these attributes are synced between on-prem and cloud.
Using on-prem Exchange powershell, I run the following command:
New-DynamicDistributionGroup -Name "DG_NH" -RecipientFilter {((RecipientType -eq UserMailBox) -or (RecipientType -eq MailUser) -and (CustomAttribute6 -eq 'Y')} 
This correctly finds the 2 users when I query for them as follows:
$DDG = Get-DynamicDistributionGroup DG_NH
Get-Recipient -RecipientPreviewFilter $DDG.RecipientFilter | FT alias
So I then delete this DG, and recreate it this time looking at the multi-value attribute ExtensionCustomAttribute2, as follows:
New-DynamicDistributionGroup -Name "DG_NH" -RecipientFilter {((RecipientType -eq UserMailBox) -or (RecipientType -eq MailUser) -and (ExtensionCustomAttribute2 -eq 'NH')} 
Replaying the query above, I can see this also works fine and finds my two users.
Next I open a new powershell and connect to Office 365 and repeat the process there.
New-DynamicDistributionGroup -Name "DG_NH" -RecipientFilter {((RecipientType -eq UserMailBox) -or (RecipientType -eq MailUser) -and (CustomAttribute6 -eq 'Y')} 
This correctly finds the 2 users when I query for them.
And then delete the group and recreate it using the multi-value attribute:
New-DynamicDistributionGroup -Name "DG_NH" -RecipientFilter {((RecipientType -eq UserMailBox) -or (RecipientType -eq MailUser) -and (ExtensionCustomAttribute2 -eq 'NH')} 
When I run the query this time it produces no result.  Every test I try results in an empty group if I am using a multi-valued attribute in the search criteria in the cloud.  If I use single valued attribute, it works fine.
I really need to be able to get multi-valued DDG's working in the cloud.  If anyone has done this and has any suggestions, I would appreciate seeing what you did.  And if this is the wrong forum to port this, if you can point me to a more suitable
forum I will report there.
Thanks,
Richard