SX-50 system

When I set up a couple of trunk lines last spring everything was working fine. Now, for some reason, If a call is using trunk one and a second call comes it, it gets a busy signal instead of using the second trunk. I am not sure what changed or where to even look to see whats going on. If a call is using the 2nd trunk line and you call into the system it will ring the console like it is supposed to. Is it on the telco side to setup the hunting or on the sx-50 side?

Any ideas for me.

Thanks