Hi there!
1. Analyze the NTP log (
/var/log/ntp.log) and find that connections are refused due to inconsistent ports.
2. Run the chkconfig -list | grep fire command to check the firewall settings.
Solution
Step 1. Uninstall the standby OMS.
Step 2. Disable the firewall.

Step 3. Reinstall the standby OMS.