Hi , I`m JackPerhaps I can help you with this problem
I take it that this dish box (receiver ) is made (dual output) to have a second tv connected to it through a coax cable ?
Also , could you please give me the tv`s model number ?
You had this same tv connected at the same location with the same wiring ?
From your opening post I quote " I am hooking a second tv to our dish network " , this usually means a new setup but now we are talking about troubleshooting a sudden problem so I will opt out as I don`t have time for this now .
You don`t have to do anything , your question will be reposted for other techs. to see and jump in.