Resolution:
The LDAP Adapter Schema, by default, will not include the Operational attributes.

The solution is to manually add these operational attributes in the adapter project to perform any operations using the LDAP Adapter.

Below are the steps to be followed:

1. Open the adapter project in Designer.
2. Go to the AESchemas folder - ae - adapter - LDAP - LDAP_domainName AESchema - Object Class schema - Object Class - Go to the Object Class Attributes
3. Right-click Add Resource Adapter Schemas - Generic Sequence
4. Modify the name to 'modifyTimestamp'
5. Point the sequence type as sequence string.

The LDAP Adapter will now be able to retrieve the operational attribute(s).