Skype shows an error message and does not start.

Hi, I use Skype for web calls. For some days I am not being able to start my Skype and getting the following error.
I have restarted my PC and still getting this error message and not being able to start Skype.
Please give me a solution to this problem.
I also use a Skype phone.

Error message: Can't open Skype. You are already signed in on this computer. Please sign out and try again.
