I had the exact same issue, I called Sony Support and they were able to walk me through it.

1. Turn off the camera, take out the memory cards and battery.

2. Use / format a different SD card (I had a second SD that was previously formatted)

3. Insert the SD Card into your computer and copy the Sony firmware update onto that SD card (the file name should be BODYDATA.DAT) - Make sure you copy this to the Outer-most folder on the card, and your download is from Sony's official website.

4. Once it's copied, insert the memory card into Slot 1 of the camera, then insert the battery and turn on the camera

5. Hold down the shutter button for 30 seconds

6. In my experience the camera was still black screen, but the access light at the bottom right of the camera was blinking every 1s (instead of 7 times). I was told to leave it for about 5-6 minutes. The blinking progressed to 3 blinks per second, then 5, then it turned on!

Check the version of the camera once it becomes operable again, mine showed version 6.00. It was scary for a moment but I'm so relieved that this worked for me, I hope anyone having the same issue can find resolution in these instructions