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In the Application log of the Event Viewer - it reports on the success and failure of drive mappings. Usually the issue is clear based on the contents of this log. Sometimes it says "access denied" therefore meaning a clear permissions problem (not in the right group(s) or not given rights to the directory). If there are no reports of even an attempt to map the drive then the most likely problems are that either the computer object is in the wrong OU or the user is not matching the criteria of the drive mapping targets set by Group Policy Preferences. This second scenario would most likely mean the user is not in the right Active Directory groups to get the drive mappings and would require escalation to NIT/EUC.
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The Windows Helper App includes some basic drive mapping troubleshooting help:
Get drives currently mapped by clicking Troubleshooting > Network Drive Status
Attempt to remap all drives by clicking “Reconnect Network Drives”
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