Exchange 2013 to O365 Hybrid migration problems

Use the "users with errors" view, invalid/missing attributes synced from on-prem can cause the object to be present in WAAD, but Exchange Online will still complain about those attributes. You can get the same info via the WAAD PowerShell module:

Get-MsolUser -HasErrorsOnly

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Other than that, check the value of the CloudExchangeRecipientDisplayType parameter. If the user exists in WAAD and everything is in order with the attributes, the issue might be with the so-called forward sync (in other words on the issue is on MS side), so you can open a case in order for them to take a look.

For the federation cert, you can ignore the warning. It's a known issue with the BPA.

Ah ha. I see them showing as Contacts in exchange. But don't know how to get them as Mailboxes. Checking on the attribute issue. But I am confused because one article says they should be 1073741824 and another is showing as -2147483642 and another says -2147482106. So i am not sure what the right answer is.

User mailbox is 1073741824. -2147483642 is synced mailbox user. -2147482106 is synced remote mailuser.

But you cannot control this *after* the sync. Contacts will always sync as contacts, if that's what you have on-prem it's normal.

But these are not contacts. The mailboxes on Exchange are showing as contacts on O365. So what value should they be? I can't migrate anything until they show up as mailusers.

The only way I can think of causing mailbox-enabled on-prem users to sync as contacts is if you have made some major modifications to the sync rules. If this is indeed the case, you should re-evaluate those rules or do a clean dirsync install to restore the default configuration.

Have you assigned licenses to the new users? Just DirSyncing them will not create a mailbox, They need to have a license assigned.

Yes. I assigned a license, and then migrated, and still showing as a contact.

I think the more important question here is how do you assign a license to a Contact object? Those do *not* have a corresponding user object in WAAD, so I'm a bit lost here.