We are using Active Directory to synchronize user information to Microsoft 365 and HENNGE Access Control.
When using the HENNGE Directory Sync Tool to synchronize the accounts, the following error appeared:
Exception calling "ToBase64String" with "1" argument(s): "Value cannot be null.
and the synchronization cannot be done successfully.
When HENNGE Directory Sync Tool is used to synchronize the account information, the "ms-DS-ConsistencyGuid" attribute is ensured to map the account correctly by the default setting.
This attribute is also used to map the account to Microsoft 365 via Azure AD Connect; if the federation is done with HENNGE Access Control, this value called the "ImmutableID" is required to be the same on the HENNGE Access Control as well.
If the Azure AD Connect is installed and executed correctly, the "ms-DS-ConsistencyGuid" attribute value should be populated automatically; however, if the permission is not correct or sufficient, the value may be left empty.
Under those circumstances, [Exception calling "ToBase64String" with "1" argument(s): "Value cannot be null.] the error will be shown.
If those errors occur, please perform the following check to ensure that the "ms-DS-ConsistencyGuid" attribute is populated with a value.
If the value appears empty, please install the Azure AD Connect and execute the program in order to populate the "ms-DS-ConsistencyGuid" attribute with value.
※ For the specification or details related to Azure AD Connect, please contact Microsoft Support directly.
This article was written in October 2019, the specifications of Microsoft 365 or Active Directory may be changed at any time.