Wordpress Users Not being Added To Contacts

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I am not sure when this issue started, but I recently tried to Synchronize my Wordpress users to CiviCRM contacts.  The script runs fine, and tells me:

Synchronize Users to Contacts completed. Checked 46 user records. Found 46 matching contact records. Created 0 new contact records.

I know I have users in Wordpress who are not in CiviCRM contacts, and they are not being added.  No errors are generated when I run the script (with Debug on).  I have a number of CiviCRM extenstions installed, and I am not sure if perhaps one of them is causing the problem.  I have had some issues with the extensions.  ANy help on resolving this greatly appreciated.

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Any help on this?