So I updated the Focusrite Control Software to the latest version which is 2.3.3. No it shows No Hardware Connected when I bring it up. Everything is still working with the routing but there is no visual of it if I need to change anything. So the hardware is working but not the software. I went to the Focusrite site and with through there trouble shooting on the subject. All is listed fine on my computer. Also tried another usb port and it does come up once. But if you close the Focusrite Control it shows up No Hardware Connected the next time you open it. Tried turning the anti virus off as well and no luck. It was all working prior to the update. I am using Windows 10 pro. Have put in a request with them but it usually takes a little while to hear back and thought somebody might know what to do. 

Is the unit fully online before you open MixControl? I forget if it updates itself if it comes online first, but it does when you power the unit off.

After checking the usb cable ,I recommend to do a full new driver Installation .
First Disconnect the Interface -desinstallation -
New Start -
Installation of the drlver -
Nee Start -
Connecting the Interface
Hope that helps

 
I tried installing and reinstalling several times and the same thing. Well at least I am still able to use it but can't change any of the routing.  Also my computer is always connected to the net. 

I am having the same issues after the update to version 2.3.3. I can't open mix control - it ether crashes or just prompts "no hardware connected". I experience this issue on my Windows 8.1 PC and Windows 10 laptop. I also did all of the troubleshooting provided by Focusrite, in fact it wasn't even necessary because all my setings were ok according to the instructions.  I really hate this company. Since I bought the Scarlett 18i20 I have encourted notorious problems with playback or just basic things which shouldn't be a problem - like this one. 

My problem is solved. They got back to me today and had me download version 2.3.2. Now it works fine. Try downloading that. I really haven't had any problems up until downloading the latest version. Let me know if that works for you.

Where can I download 2.3.2 version? I can't find it on Focusrite's website.

Ya I don't see it on there either. They sent me a link for it and downloaded it from there. Try contacting them. It won't let me post a link on here because I don't have enough post points. 

Well I could, but I am in a hurry to be honest. Maybe you could send me PM?

Sent you one. Let me know if it works.