Try setting the Squelch to 0. Also do you have both sites programmed in?The road trip I took yesterday confirmed that my SDS-200 works as advertised. I can pick up Chester County's P25 system in New Castle County fine, just not at my home QTH.
It is the terrain as I am on the reverse side sloping down away from ChesterCo.
I drove up to Bethel Twp in Delaware County and up to US 1, back down 202 to Naamans Road (DE92) and had a strong signal until I went into the dip at Foulk Road (DE261). I used the supplied whip antenna and the 120 volt wall wart into an inverter in my truck. With the supplied antenna, I receive a two-bar signal in my house but no audio.