After upgrade, the MC console to 15.3.0.6713 The agents status is showing connected, waiting for server response and for new enrolling the devices it giving an error Enrollment failed, please retry or contact your system administrator. This issue has happened to the entire production device.
Once we disable the file sync rule all the agents are back to normal(agent status-connected) and we are able to Enroll new devices.
In our environment, the File Sync rule is used to run the script (enabling the Default application in AE devices).