Using ueberauth and guardian to implement Auth, I get the token, but when I put the token in the header to access other routers, it still {"message": "invalid_token"}

I haven’t used Guardian, but the token should probably be sent as a “bearer token” in the Authorization header. So I suspect you have to set the Authorization header value to “Bearer eyJhbGciOiJIUzUxMiIsInR…”