PCs that we determine cannot run Windows 10 will not see the Get Windows 10 app before July 29th. After July 29th, we’ll enable the icon in the system tray. This is to help ensure that you can easily check your PC’s compatibility if you choose
http://answers.microsoft.com/en-us/...i/848b5cce-958b-49ae-a132-a999a883265b?auth=1
Scroll down to the accepted answer. If none of the suggestions work, it may be due to this:
It's also possible that not all required updates are instslled. I have windows 7 and all important updates installed and still don't get it he icon. There are updates required for it to appear but it's possible the are optional updates.