Let's try doing a clean install and delete all the cache of the program. Uninstall your software first, then go to the folder location below on your computer then delete the Voxal folders:
C:\ProgramData\NCH Software
C:\Users\(Your computer profile)\AppData\Roaming\NCH Software\Voxal
If you can't find the AppData folder, set Windows to show hidden files and folders with the steps from this link: https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files.
After deleting the Voxal folder, restart your computer then install it again from the next link: https://www.nchsoftware.com/voicechanger/vxlsetup.exe