Problem sharing with one external user.

Good morning!

Before I get to the actual problem I have, here's a short description of my setup.

Using SharePoint Online, I've created a site collection specifically to contain sites that will be shared with external users.  All of the sites have their own unique, default group to which external users are added when the invitation is accepted and they login using a Microsoft account.  Other than that, they all have identical security groups.

The problem I'm having is with one specific external user.  Before it was reported to me, I'm told that the person received the invitation but had some difficulties logging in.  She tried two different email addresses that were associated with a Microsoft account, but one didn't work and the other didn't give her correct permissions (even though the correct group was selected when sending the invitation).

When I started investigating, I made a few observations that seemed strange.

• All of the other external users had account names in the format i:0#.f|membership|live.com#username@domain.com, but this user's wasi:0#.f|membership|username_domain.com#ext#@companynamecrm.onmicrosoft.com.
• In the Office 365 admin center, this person shows up in the Active Users list but none of the other external users do.
• If I create a new sharing invitation, start typing the user's email address and hover over the autocomplete result, I see this:
  1. <email address>
  2. Tenant
  3. <username_domain.com#ext#@companynamecrm.onmicrosoft.com>
• But for the other users, I see:

1. <email address>
2. Extranet Users
3. <live.com#username@domain.com>

Further attempts at inviting this person result in non-receipt of the invitation.

Has anyone seen something like this? Any suggestions on how to get this user added correctly?

Thanks in advance for your time and any guidance you can provide.

Chris