It has been identified that after upgrading from DLP 15.0 to 15.0 MP1, Active Directory integration data (or any other previously setup authentication data) is being stripped from the WebUI XML file. Symantec provides the fix via the below article, but I put these steps together for Appliance Customers.
1.SSH to enforce as appuser after upgrading to DLP 15.0 MP1
2. Switch to protect user
sudo su - protect
3. Backup the old springSecurityContext.xml file.
mv springSecurityContext.xml springSecurityContext.xml.BAK
4. Navigate to the DLP 15.0 backups
5. Extract the backups
tar xzf SymantecDLPEnforceBackup_126.96.36.199028.tar.gz
6. Navigate to the backup springSecurityContext.xml file... Please note that this directory path is a backed up version of the working /opt/SymantecDLP director before the upgrade.
7. Copy the backup xml file to the production location
cp springSecurityContext.xml /opt/SymantecDLP/Protect/tomcat/webapps/ProtectManager/WEB-INF/
8. Set ownership and permissions for springSecurityContext.xml
chown protect:protect /opt/SymantecDLP/Protect/tomcat/webapps/ProtectManager/WEB-INF/springSecurityContext.xml
chmod 750 /opt/SymantecDLP/Protect/tomcat/webapps/ProtectManager/WEB-INF/springSecurityContext.xml
9. Restart VontuManager service