Firmware Upgrade for S120 not effective

Hallo,

I am having Sinamics S120 CU310-2PN drive. I was having firmware version 5.1 for the drive and running. I decided to upgrade to 5.2 and did the steps as mentioned in Instructions_Firmware_Update_S120.doc in https://support.industry.siemens.com/cs/ww/en/view/109762626 

Few things I did in sequence are 

1) In Starter, I checked for the firmware upgrade and found 5.2 and upgrade it. Got an "updated" message at the end.

2) Copied the 5.2 firmware to the flash card and put it back to the CU unit and powered On.

3) Tried to go online but it failed with the error as - Not possible to connect to device of type 5.2 to hardware of type 5.1 . The screenshot is attached here.. 

4) As mentioned in the Instructions_Firmware_Update_S120.doc, I couldnt see an automatic update of the firmware. ( scrrenshot is also attahced)

What could be possibly go wrong? 

I am using flash card - CF 6SL3054-0EH00-1BA0

My PLC is S7 1500 and I am using TIA 15

I am using Starter 5.3 version to configure the drive. 

I suppose you still have a V5.1 Version  《maybe a newer hotfix then before》on your CF card. Can you open the content.txt File from the CF and publish the "Internal version" ?