URGENT Import: How to re-attach user's archive account?

I have the following scenario in old system:

• user@domain.com has archiving enabled.
• archive account is called user-20170524@domain.com-archive

In the new system:

• user@domain.com has archiving enabled, but it does not work.
• user-20170524@domain.com-archive has a GREEN STAR next to the account.

Question:
How do I re-attach the archive account onto the user's account?

kind regards
aubrey