This could happen when the application gets corrupted. I suggest you re-download the latest version that's also Windows 10 compatible and install it that way. The registration key will work since they don't have an upgrade system to obtain a new system in case you're installing a new version.
Access the download page, re-download the installation package for AVS Audio Converter and then run it. Make sure to use Run as Administrator. Also, if you have any other version lower than the latest one (8.4), then you should upgrade.