Assuming this is the system we're talking about:
https://www.radioreference.com/apps/db/?sid=6919
based on the FCC license data (which may or may not be 100% accurate as always), it appears the county is served primarily by a very large single simulcast cell. Based in the license data, this simulcast cell consists of as many as 20 separate transmitters/towers under 4 licenses (see map below).
WQMG397 4 sites - Foster City, Redwood City, San Mateo City, San Carlos
WQMG398 6 sites - Woodside, Rural San Mateo(2), San Gregorio, La Honda(2)
WQMG400 4 sites - Brisbane(2), San Bruno, Woodside
WQMH682 6 sites - Half Moon Bay, Montara, Pacifica, Pescadero(2), Rural San Mateo
Each of these transmitters uses the same 10 frequencies (the RRDB information matches the license information for the simulcast site). If that is the case, this fact alone is going to make it extremely difficult to receive the system with most scanners.
Digital simulcast systems are much harder to receive in most cases than older analog systems (simulcast or not).
On a recent trip to look closely at the York County PA 700 Mhz system, my GRE PSR500 (PRO651 equivalent) - which I use 99% of the time to drive Pro96Com to view the system operation - was pretty much useless. Eventually, I swapped out the PSR500 for a WS108x and things were much better - at least for seeing the system on Pro96Com. It still is unclear to me exactly what the difference was causing these issues on the PSR500.
As far as the data on the RRDB being just copies of information from the FCC license -- that doesn't seem to be the case. The FCC license doesn't provide any information about which system/site frequencies are control channels or site/neighbor data.
However, there are some oddities I see with the site frequency data that is posted on RR. Primarily that there are 3 sites (probably isolated/standalone) that are showing using the same (or nearly the same) frequencies (Brisbane, Towne Ridge, Pointe Montera) as well as 2 other sites (Pigeon Point, La Honda) also sharing the same (but different from the above) frequencies. This could be just fine if those sites are so remote and isolated that there is no chance they can conflict with one another - it's just not something I've used to seeing.
These 5-6 (probably) stand-alone sites are sites you will probably want to stay away from if that are correct and really as "remote" as they seem. Chances are they will be fairly easy to receive but carry very little traffic (but I am
seriously speculating since I'm on the other side of the country).
In terms of troubleshooting - just to see if the system can be received at all, I'd focus on the countywide simulcast site - determine which frequency is the active control channel, and only program that frequency into your configuration.
Next, I'd try getting as close to one (and only one) or the transmitter
active sites (note: just because the license says they have 20 towers/transmitters in the simulcast cell/site doesn't mean all of the towers are live).
Depending upon the results, there are other things to consider and try.... but you'll want to limit those things as much as possible while trying to figure things out.
I (WE) just don't think the RRDB is correct maybe frequencies are correct but how it configures the radio talkgroups, etc.. in the radio is incorrect? I don't know..
