That issue should have nothing to do with registration. Install the latest version, registered or not, to test.
What is your 'recorder' and how, exactly, are you transferring its content to Videopad? Please share the recorder file that has audio. It's easy, and can be done privately.
Just upload the file/s to a free server, such as Google Drive or MS OneDrive, get a shared (public) link, copy the link and paste it here or to me in a Private Message via the mail envelope in the top-right corner of this forum. When using Google Drive, if necessary change "restricted" to "anyone with link can view."