Probably because the site you're listening to doesn't broadcast a bandplan. They had the same problem in Orange County, Florida with their G5's and Unication. Unication's stance was that all sites should broadcast a bandplan and the system was broken.
However, according to Page 68 of this document
https://www.repeater-builder.com/tech-info/pdfs/p25-training-guide.pdf, the site is probably operating in Implicit Mode and the radio relies on it's own internal programming to determine what frequency to tune to.
You'll have to see if any sites in your area transmit a bandplan and program your Unication to only use that site.