Hello. I had the same problem as you, but was able to solve it here.
Essentially it came down to us accidentally compiling the project as a JavaScript project and then changing the plasmic.json from js to ts. But that wasn’t enough.
I break down my full problem as well as our solution in the linked topic. Hopefully, our problems were similiar and you get the help you need. I completely understand how frustrating this is because I was creeping on your post for about a week before we just solved it.