IBM Notes client user cannot manually Archive any documents or access their mailfile Archiving Settings.
When accessing "Actions" -> "Archive" -> "Archive Settings" then the error message "Invalid or nonexistant document" is displayed.

The users Archive profile document is corrupt.
From workspace hold down Shift and Ctrl keys and then open the users local Address Book (Contacts).
Additional views (which are usually hidden) will be displayed on the left hand navigation menu.
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Select the ($policies) view.
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Select All documents in the view.
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Delete them.
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Close the Contacts database.
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Restart the Notes client.
Then access the Archive Settings again. The error message should now no longer be displayed.
The client may not have downloaded the policy settings yet. They should come down over the next few client restarts.