Though the issue may seem to be the same, there are a number of reasons for audio loss described in this thread.
Install this version, for now. Ignore any virus prompts. If it succeeds, suggest waiting a week or so before installing the latest release.
What version of VP is being used? Try the latest. For licensed users upgrades are free for up to six months from purchase date. After that, VP will continue to fully function but a fee will be required in order to register the newest. Retain your old install file and registration info.
How large are these files and at what resolution?
If a newer release doesn't solve the issue, please share a single file here (or in private) and someone will take a look.
Just upload it to a free server, share it (make it public), get a shareable link, copy that link and post it here or to me in a Personal Message (click the folder at the top-right of this forum and search for "borate.")