badar14,
I had similar if not the exact problem you are having right now. IRCC web form will not help you, as they will only explain the potential causes for not being able to link to your MyCic A/C.
Try the following instead:
1) Are you using your parents (primary applicant's last name) and application number?
I the answer is "Yes". Check your primary applicant's name on his/her passport. If the passport does not specify "last" and "first" name, then CIC will use the whole name as "last name".
If that is indeed the case, use primary applicant's the entire name as his/her "last name".
2) Then enter the application number (if using last name and application number).
3) As for numbers of family members, they do not count kids. So, try 4.
If that does not work, try 3. I was trying 4 (me & my wife + parents = 4) to link my application and did not work. It turned out that CIC did not count my wife and kid. So, as odd as it may be, the "odd" number - 3 - might just work for you.
Good luck!