Sudoku solver : no output

I am getting no output for my code.
Please look into it.
Also provide me of some good idea about solving this question and judge my approach.

Pls send me the ide link

Use the backtracking approach

I hope I’ve cleared your doubt. I ask you to please rate your experience here
Your feedback is very important. It helps us improve our platform and hence provide you
the learning experience you deserve.

On the off chance, you still have some questions or not find the answers satisfactory, you may reopen
the doubt.