I was there about 3 weeks ago, and the VHF frequencies were alive and well for Coconino County Sheriff. I can't imagine things have changed that quickly, but you never know these days. The DB should be current unless there was a major change in the last few weeks.
I have not noticed anything different on the analog posted CCSO frequencies. I am listening to them now from my Northern AZ home location. Flag PD et al are on trunked system although I am not hearing that much NAU traffic for a while.
I usually listen to 155.49 and 155.835. I suggest not using any CTCSS tones due to the varied location of the repeaters . Perhaps you are missing transmissions due to your use of a repeater tone far from your location.
Can you confirm that you can receive other active frequencies in your area? Fire departments, DPS, ADOT, AZ Game & Fish, Coconino (Prescott, Kaibab) National Forest, Hams, aircraft, businesses?
What antenna are you using? If it's outdoors, when was the last time you inspected it and the feedline? Do you have a volt-ohm meter or an antenna analyzer to test the coax and the antenna?