receive phone calls on my iMac

Before 2 days I could receive and call from my iMac to my iPhone and Reverse .

After 2 days of unused iMac ( Was after shut down ) , I powered it on ,

All OK except when opened iTunes to see if there is an updates, A pop up windows appear to fill my Apple ID Password .

(Although iTunes was connected to my Apple ID and I see all my account .)

Also, I've mede an App password my iCloud account as requested by another pop ups windows .

Now , I can open my iMac's FaceTime app and make a call to my iPhone and face time.

But when I receive a phone call to my iPhone , I don't see any notification on my Mac..

If it works from iMac to iPhone , how can i make it in opposite way ?

All devices are up to date .

iMac 10.10.2

iPhone 6

Thanks .