This error typically occurs due to one of the following reasons:

Soundtoys isn’t the only brand that uses strict folder structures—let me know in the comments if you’ve seen similar issues with iZotope or Waves.

Ensure both TEMP and TMP are set to the default: %USERPROFILE%\AppData\Local\Temp .

Similarly, try running your DAW (e.g., Ableton Live , FL Studio, or Cubase) as an administrator once to allow it to initialize the plugin folders.