Cortana only replies "Sorry, I didn't get that". How do I fix?

Cortana returns Bing results using Microsoft Edge.  Without Microsoft Edge (which uses Bing) allowed thru firewalls, Cortana will not have many results.  Microsoft speech recognition will need to be working also for those of us who use blanket deny type firewall systems or hosts files, which may block speech recognition as well as Edge and hosts process.  As long as the speech recognition is working, and the host processes for windows services are working and allowed thru your various firewalls, and as long as you're online (you need to be online for Cortana to get speech recognition results, or else it won't be able to do anything) you should be able to say "Hey, Cortana open notepad" and it should take a minute to run the notepad program.  Which is a good test to see if it works.

I finally found the problem, the microphone was turned off.

Your last recommendation ended up changing  my whole computer!!! I got very frustrated , so I bought a new one.  I'm am now imputing all my personal information.  It's a lot of work, but the new one is so much faster.

Thanks for your help, Ed

Enable Voice activation in privacy settings.  This will make it so your Hey Cortana toggle in cortana settings will go on.  Without Voice Activation enabled, there is no way to get the Cortana toggle to stay in the 'on' position.  

Above the voice activation settings in privacy settings, are the microphone settings, this also has to be enabled for the Cortana app.

Cortana returns Bing results using Microsoft Edge.  Without Microsoft Edge (which uses Bing) allowed thru firewalls, Cortana will not have many results.  Microsoft speech recognition will need to be working also for those of us who use blanket deny type firewall systems, which can block speech recognition as well as Edge and hosts process.  As long as the speech recognition is working, and the host processes for windows services are working and allowed thru your various firewalls, and as long as you're online (you need to be online for Cortana to get speech recognition results, or else it won't be able to do anything) you should be able to say "Hey, Cortana open notepad" and it should take a minute to run the notepad program.  Which is a good test to see if it works.

You don't have a hardware problem with your laptop.  Just use another app and test your microphone.  Don't send your computer in to the manufacturer that's a huge waste of time and resources.

the harder you work the luckier you get

Cortana returns Bing results using Microsoft Edge.  Without Microsoft Edge (which uses Bing) allowed thru firewalls, Cortana will not have many results.  Microsoft speech recognition will need to be working also for those of us who use blanket deny type firewall systems or hosts files, which may block speech recognition as well as Edge and hosts process.  As long as the speech recognition is working, and the host processes for windows services are working and allowed thru your various firewalls, and as long as you're online (you need to be online for Cortana to get speech recognition results, or else it won't be able to do anything) you should be able to say "Hey, Cortana open notepad" and it should take a minute to run the notepad program.  Which is a good test to see if it works.