In this case, the main difference between versions is that The "Master's Edition" registration will give you unrestricted use of MixPad, including unlimited tracks. The "Home" registration does not have the VST plugins and is limited to 16 tracks only.
Now there is no lime for the time, so how big is the file that you load, 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 MixPad folder folders:
C:\ProgramData\NCH Software
C:\Users\(Your computer profile)\AppData\Roaming\NCH Software\MixPad
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 MixPad folder, restart your computer then install it again from the next link: https://www.nch.com.au/mixpad/mpsetup.exe
That should do it. Please try it again after that and see if that fixes the issue.