When I am going to any questions on Stack Overflow, that time edit button is appearing as disable. I can't click on it because there is no link of editing. Can you please help me what is the problem?
This is normal. Sometimes the edit link is not enabled because another user who has less than 2K reputation has just suggested an edit on that post. So unless that suggested edit gets reviewed, the edit link is not enabled for other users below 2K reputation.
But if you are getting a disabled edit link on all questions and answers, that means too many of your suggested edits got rejected and you can't suggest edits for the next 7 days.
For other reason please read this answer.