5G UW Not Ready

[jonbruce_vzw]

5G UW although it shows on coverage maps, and my reports 5G UW service, my phone has zero connectivity when it picks it up.  Recommendation from local Verizon store was for me to set the phone to use LTE only, as the service is unstable in our area.  This is Marin County, just north of San Francisco.  Note also precisely the same behavior in the city of San Francisco, so I doubt this is localized.