Try this (ensure that Audacity is not running before you start):
- Download “Audacity 2.2.1 zip file (11.57 MB)” from https://www.audacityteam.org/download/windows/
- Unzip (extract) the contents to a suitable location on your local computer where your standard (non-admin) log-in has read / write access. (if you’re not sure how to do that, ask).
- Open the extracted folder and find the file “audacity.exe”.
- In the same folder as the file “audacity.exe”, create a new folder and name it “Portable Settings”.
- Double click on the file “audacity.exe” to launch Audacity.
Do you see the full list of Nyquist plug-ins in the Effect menu?