I have been struggling with this problem for many years. I am surprised, no one faced this issue. While I was writing this question, I found the solution.
I had an Editor control. The problem was that the copy/paste menu did not appear in certain cases. It couldn't figure out and this issue remained open since year 2014.
Cause: When I used to set text to this control inside this editor which wrapped to another line, then the copy/paste menu did not appear.