Please check the following files
Ensure the AntiMalware.ini file has the internal LUA details
/opt/Symantec/sdcssagent/AMD/system/AntiMalware.ini
Check lux.log file
/opt/Symantec/sdcssagent/AMD/stargate/logs/lux.log (It will have all LUA connection attempt details, you'll be able to see whether the Agent is trying to connect to LUA at all and what the return code is.)
If no Internal LUA information. Restart the sisamdagent
systemctl restart sisamdagent