How did the people of Ephraim and Manasseh treat the couriers bringing Hezekiah's Passover invitation?

Answer: Scorned and mocked them

The couriers were scorned and mocked, yet some from Asher, Manasseh and Zebulun humbled themselves and came to Jerusalem.

“And the couriers traveled from city to city through the land of Ephraim and Manasseh as far as Zebulun, but the people scorned and mocked them. Nevertheless, some from Asher, Manasseh, and Zebulun humbled themselves and came to Jerusalem.”— 2 Chronicles 30:10-11 (BSB)