Your migration failed checking Source credentials - User CN=xxxxxx/O=xxxxxx cannot open database MailServerName!!PathOnMailServer\DatabaseName, where CN=xxxxxx is the Commmon Name of the mailbox, O=xxxxxx is the Organization the mailbox belongs to, MailServerName is the name of the mail server, PathOnMailServer is the path on the mail server the database is located in, and DatabaseName is the name of the database, may be caused by the following:
Confirm that one of these scenarios may be the issue by performing the following steps:
Confirm that the NSF database exists in the location shown in the MailFile column of the corresponding Source Email experiencing this issue.
If the NSF database exists, double-click to open it and confirm that the migration account is listed in the NSF Access Control List by clicking on File> Application> Access Control. If the migration account is part of the Access Control List, highlight the account and make sure Manager permission is set in the Access drop-down field to the right of the list, and all permissions boxes are checkmarked.