Permission management can't resolve username

I am trying to use Action Pack to manage item level permission on a document library on a new SharePoint Online environment.

All attempts to run Grant action returns error message: Exception: Can’t resolve the username

Example:
Action: Grant Edit permission on item Current Item:ID in list Workflow Context:List Name to user or group geir.mathisen@skill.no
Terminates with: Exception: Can’t resolve the username: geir.mathisen@skill.no

But the email address is a valid user, and works perfectly if I try to grant access using the SharePoint standard interface.

If I run the same action, but granting access to an existing SharePoint access group, it works fine.

Any idea what might be causing the WF action to not like this?
Thanks

Hello Geir,

I see that you use username geir.mathiesen@skill.no, could you please clarify it is external user or your domain has been configured with support AD FS?

I am logging on to customers O365 environment using my company O365 account.
I guess that means the domains are federated (but this is not my area of expertise).
Geir

We seem to have resolved this situation.
It seems to be caused by the fact that WF actions were running in context of a userid external to customers AD.
When running with a AD defined userid names are resolved as expected.
Case closed.

Geir,

Thank for sharing your experiences, I’m really appreciate it.