Yes, you can participate in the 2nd round of CDAC counselling even if you didn't submit any choices in the 1st round.

The second round is open to candidates who:

• Didn't participate in the 1st round at all.
• Participated in the 1st round but weren't allotted a seat (their rank wasn't high enough for their preferred choices).
  
  In the 2nd round, you will only be eligible for seats that are vacant after the 1st round allotment.
  
  
  https://it.careers360.com/download/ebooks/cdac-c-cat-complete-guide
  
  I hope it helps!