SINAMICS CU310-2 PN fw 4.8: X127 Port not responding to communication

I have a SINAMICS CU310-2 PN drive and as per the requirement of the on going project I had to update drive firmware from 4.6 to 4.8. I'm sure that firmware update was done accurately but after this update Ready (RDY) LED blinked at 0.5Hz frequency. I tried all possible solutions but it did not changed. So again I downgraded firmware from 4.8 to 4.6. Now LED is ON continuously but X127 port does not respond for communication.  I tried parameter settings and all the IP related settings. Still problem is here. Plz help me to solve this. The project is urgent.

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Split from CU310-2PN firmware update error.