I think I can also see what has gone wrong in a way - the uninstall file has been cleaned up by something (a windows upgrade maybe)?
So, here's next steps:
Download 3.1.5092 from https://d.sharpcap.co.uk/download.html? ... 3.1.5092.0.
Try running the installer. If it offers uninstall, choose uninstall and see if that works. If it offers install try that.
If neither work, try unzipping and running the attached msi, which should be the correct version and should offer to uninstall for you.
Hopefully this will make at least a little progress and we can then keep moving forward.
cheers,
Robin