Factory default reset not help indicator is flicking. what to do ?

See Flashing Green or Amber here > AirPort base stations: About AirPort base station status lights (LED)

A persistent, flashing amber light indicates that any of the several potential conditions may require your attention:

• The base station has not yet been configured because it is new, or the reset switch has been set.
• You have selected a security configuration that is not recommended.
• One of several other conditions, such as a disconnected Ethernet cable or invalid IP address has been detected.

To find out why your base station's status LED is flashing amber:

• Open AirPort Utility
• Click on the AirPort base station
• Look for a Status setting in the small window that appears
• Click on the small amber dot there and another window will open to explain what the "issue" might be.