I finally got my project to build and execute with Reaper (so consider my question here solved - I had apparently changed the Debug executable directory from what it’s supposed to be), but the plugin crashed almost immediately after startup, during a call to the SetState function from the VST3 SDK. The problem turned out to be that an old saved parameter value from the last time I built the VST3 version was being loaded into a parameter which did not accept that range, which down the line led to the program trying to access index -1 of a vector, hence the exception.
Is there a command or script to erase and reset all previously serialized parameter values when building, loading the default values instead? (I feel like I might have missed something obvious, as I’d imagine this is a common issue.) The plugin runs fine in new Reaper projects that have no serialized values associated with them, but if I just delete the RPP file in my project folder, the plugin doesn’t load.