@AddisonDeSaulenet unfortunately the output when there is an error in the post build script isn’t very helpful.
The most common issue is that there is a problem with loading or unloading your VST3 plugin. The post build script actually loads your plugin straight after you build, this is so that it can generate a file called “moduleinfo.json”.
In the topic you linked, did you try to follow the steps outlined by @cblessing?
Suddenly can't build vst3 in Windows...|Error|MSB3073|The command copy /Y - #16 by cblessing)?
If however you think it might be a problem with copying the plugin you can try disabling the plugin copy step in the Projucer to see if the error goes away?