Make sure that in MA policy you uncheck the box 'Accept connection only from ePO server'
Yes, it has already been unchecked.
perhaps firewall or the Agent service needs a restart?
restart your McAfee services and try again. (sql included)
Upgrade the agent extensions to up to date and check again
Try to do a telnet connection on port 8081 from ePO server to a client.
Is the connection is open ?
What is the error on IE? You have a connection timeout? Or you cannot find the page?
Are the IE settings the same for all your machine? It could be also a proxy exclusion problem.
Thanks all for your input.
We have found out the cause of this issue. It's the L7 firewall blocking the connections. After we adjust the firewall rules, it works again.
1. Telnet <ip_address>:8081 always works for this machine.
2. Only a few machine in the same subnet of this machine can open http://<ip_address>:8081 page before.