Howdy,
When trying to load a plugin using UXP Developer Tool into XD without an open document, you’ll receive an error “Plugin Load Failed” and a log “Plugin rejected - due to invalid object”. If you open a document in XD and then load the plugin again, things will work as expected.
I’m not sure if the error is technically accurate, but it’s quite confusing. I spent a couple hours testing manifests, including the boilerplate that UXP Developer Tool itself spits out, and only accidentally figured out the fix because I had switched back to the classic manual developer folder method.
)! We’re looking into it.