EVGATech_LeeM
Also, with the NU Audio program closed, try going into your App Data folder, then Local, then EVGA.  You'll see a folder that starts with NUA.exe_Url_[gibberish], and ends with a bunch of random numbers and letters.  Delete that folder, then try opening up the software again.

Thank lord I found this post, Lee! My Nu Audio suddenly stopped opening. Reinstalling did not work. 
 
I deleted the C:\users\user name\appdata\local\EVGA\NUA exe [gibberish] folder and then the reinstall worked. 
I had to open C: drive, hit the "view" tab at the top, and check "hidden files" to get to appdata. 
 
But it works again. Thank you! I think it was a weird windows problem because I a bunch of my desktop icons had randomly disappeared when nu audio stopped working but they are now back. 

EVGA_Lee
Also, with the NU Audio program closed, try going into your App Data folder, then Local, then EVGA.  You'll see a folder that starts with NUA.exe_Url_[gibberish], and ends with a bunch of random numbers and letters.  Delete that folder, then try opening up the software again.

This issued resolved the software not opening for me. Thank you!

Burke888

EVGA_Lee
Also, with the NU Audio program closed, try going into your App Data folder, then Local, then EVGA.  You'll see a folder that starts with NUA.exe_Url_[gibberish], and ends with a bunch of random numbers and letters.  Delete that folder, then try opening up the software again.

This issued resolved the software not opening for me. Thank you!

Today for me after the windows update KB5023773 (W10 Pro) the icon was missing, tried a reinstall but nothing, deleted that folder then launched the app and now it works!.

This worked for me! Thanks!

EVGA_Lee
Also, with the NU Audio program closed, try going into your App Data folder, then Local, then EVGA.  You'll see a folder that starts with NUA.exe_Url_[gibberish], and ends with a bunch of random numbers and letters.  Delete that folder, then try opening up the software again.