When the DLP admin attempts to logon, the admin is pushed to the Sys Admin role, which isn't attached to a group membership.
The DLP Admin has a group membership to the required groups that are attached to the the admin's role, the missing group membership is only missing for one admin.
Data Loss Prevention 16.x
Data Loss Prevention 25.x
The user data in the DLP Console needs to be updated.
Steps you can use to import AD users using a sync job can be found below - Import the AD Users Using a Sync Job
"To import the AD users using a sync job
1. Go to System > Users > Data Sources to display the Data Source Management screen.
2. Click Add, AD Login Source to display the Add AD Login User Source dialog.
See Adding an AD login source
3. Enter a name for the sync job in the Name field and click Submit.
4. Select the sync job and click Import. The Status column displays Done when the import completes.
Click Done to display the Import detail dialog. The dialog lists details about the import, including when the import completed and how many records were added."