UPDATE:

Hi Jeff,

As you're aware, PG&E has cut our power here near Santa Cruz and the hills
surrounding Silicon Valley, where the fact I'm able to post this means I
figured out what the problem was with the power from the generator not
getting to the house.
https://i.postimg.cc/G37D8Jq6/breaker01.jpg

I had _thought_ it was the transfer switch, simply because a couple of
those SBS-2 600V 2Amp fast acting ferrule fuses were missing, but it turns
out that when I replaced the two missing fuses, nothing changed.
https://i.postimg.cc/ryNkQQvY/breaker03.jpg

It turns out that half of the part #5 was broken inside (invisibly so)
https://i.postimg.cc/qq326cBh/Generac-Control-Panel-9067-9-16345-Page-19.jpg
o Generac Part Number #74969 35Amp Circuit Breaker

I'm not sure if that's the same part as "CB1" in bottom right of this page:
https://i.postimg.cc/Zqf00Y5K/Generac-Generator-Wiriing-Diagram-9067-9-16345-Page-14.jpg

But it's Generac Part Number 74969 35 Amp Circuit Breaker (2 ganged poles),
which disconnects 120VAC power based on my measurements on the breaker.
https://i.postimg.cc/vmTTdpdB/breaker02.jpg

This is what it says on the circuit breaker itself:
Carling Switch Inc.
AA2.B0.24.635.5D1.C
FL AMP 35
MAX VOLTS 227 (? hard to tell)
HERTZ 50/60
DELAY 04 (? hard to tell)
TRIP AMPS 43 (? hard to tell)
Mexico 9513 (probably the 13th week in 1995)

Where the complete circuit diagram is outlined already in this older post:
https://groups.google.com/d/msg/sci.electronics.repair/QhSY4KWN-Kw/P-R0-y6CBAAJ

In summary, there were two problems concurrently:
1. The fuses were missing in the transfer switch
2. Half the circuit breaker was internally broken

The result was that there was no electricity in the house when the PG&E
power went out until I replaced the fuses; and there was only electricity
to half the house. The 35Amp ganged circuit breaker has two "LINE" and two
"LOAD" terminals, where, each circuit breaker innervates half the house.

--
Solving electrical problems with advice from helpful posters on Usenet.