WebRTC between Browser(createOffer) and Unity(createAnswer)

I have a well functioning browser-based javascript client.

And I have written a unity program that receives and sends SDP protocol and Ice candidates using firebase as a signaling server.

When program runs, both unity program and browser program has set ice candidates, local descriptions and remote descriptions successfully. I have checked the iceConnectionState from both programs (browser, unity) and they are connected.

However, on the browser and on the unity, when onTrack event is called, both program’s mediastreamtrack is empty, thus the video does not display on both sides.

What are some other things that I need to try?

I would really appreciate it if anyone can share what else I can try?

(Being a new user, I could not upload the SDP, since it includes more than 2 links)