LDAP Authorization: role mapping not applied at authentication

I'm successful at mapping both Drupal roles and Organic Group roles when creating a Drupal account at the time of authentication. This much works great. However, I'm not able to successfully assign/revoke a Drupal role / Organic Group roles if the Drupal account already exits. When I run tests on users, I do get the proper group for users in the test results. I've tried to discern clues from the logs but I haven't got a grasp of what I'm looking for.

Here's some info. on my site:

• Drupal 7.16
• LDAP 7.x-1.x-dev
• Organic Groups 7.x-1.5

LDAP Server settings

• LDAP Server Type - Active Directory
• "Service Account Bind. Use credentials in following section to bind to ldap. This option is usually a best practice. Service account is entered in next section." - selected

LDAP to OG group Configuration, I am using Authorization method II.B. with the following settings:

• "Only apply the following LDAP to OG group configuration to users authenticated via LDAP. " - checked
• "OG groups are specified by LDAP attributes" = memberOf
• "When a user logs on" checked
• "Revoke OG groups previously granted by LDAP Authorization but no longer valid." - checked
• "Re grant OG groups previously granted by LDAP Authorization but removed manually." - checked

LDAP to OG group Configuration, I am using Authorization method II.B. with the following settings:

• "Only apply the following LDAP to drupal role configuration to users authenticated via LDAP. " - checked
• "drupal roles are specified by LDAP attributes" = memberOf
• "Convert full dn to value of first attribute. e.g. cn=admin group,ou=it,dc=ad,dc=nebraska,dc=edu would be converted to admin group" - checked
• "When a user logs on" checked
• "Revoke drupal roles previously granted by LDAP Authorization but no longer valid." - checked
• "Re grant drupal roles previously granted by LDAP Authorization but removed manually." - checked

Any help with this would be appreciated.