The instruction God gave to Moses at the burning bush was very clear. “You and the elders of Israel shall go to the king of Egypt” (Exodus 3:18). At the end of chapter 4, things seemed to be going according to plan.
Moses and Aaron had met with the elders, pitched the plan, performed the signs God had given them, and Israel believed (4:29-31). However, by the time Moses and Aaron get to Pharaoh, they are conspicuously alone, with no mention of the elders being with them.