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Sometimes you get odd things happening with the audio software used with your PC. I use a HP Z820 workstation as my desktop PC and when Cosworth toolbox is active the audio device manager provides a separate volume setting for it in the audio mixer software.
Try right clicking the speaker icon in the Windows status area in the lower right corner and check those settings.
On edit: It is unlikely you made the recording with valet mode active in your C7 but the PDR mutes audio recording in this mode in order to not violate state laws against audio recording of someone without their knowledge or consent. This was rolled out with later production and I think there was an update to remove this audio function during valet mode from earlier builds.
I can't use Cosworth on my pc. Something with the audio codec's it wants to use and my system don't play nice together. The file will play but I get no sound. I get sound if I play the file outside of Cosworth so it's not the file. I did some minor troubleshooting but it reached a point where I didn't want to bother - it was just easier for me to install Cosworth on a different system.