Hi @Anakin .
It is really hard to tell, but from my experience the problem is in the tracing process.
When tracing, your model produces no boxes. few things can cause this:

you are tracing with random input instead of a real image
you are tracing an untrained model (so it produces no prediction boxes)
you have some threshold somewhere which filters the predictions.

look in the code if the predictions are filtered by a threshold or NMS (Non max Suppression - may also have an internal threshold on the confidence). set the threshold to 0 so all boxes will pass the filter and see if this resolves your issue.