2010 S80 V8 No Start Condition

[Mandude]

Hi, All,
New to the forum. Still finding my way around. Forgive me if this is a topic that has been covered somewhere else, as this condition might have been seen on other P3's.
I just purchased a 2010 S80 V8 a week ago. 101,500 miles, in mighty fine shape.
It has started and has run beautifully until today. I drove it about 15 miles and parked it back at home. About an hour later I went to drive it again. I put the fob into the slot, stepped on the brake, pressed the start button and got nothing. No sounds at all, no start. The chime went off, the radio works, the lights turn on, so I'm pretty sure it isn't the battery. And there hasn't been even the slightest hint of starter trouble. It has roared to life reliably.
After pressing the start button, the CEL remains lit solid for about 10 seconds, then flashes every second for eight seconds, then remains steady on. Oil light remains on as well. No solenoid click. Two faint, short-duration buzzes (bzzt bzzt) from the engine compartment 5 seconds after the button press, likely fuel relays. (Interior lights and radio turn off for about 5 seconds after the start button is pressed, then they come back on. I hadn't noticed when it did start, but I would believe this is normal.)
I have 2 fobs. Tried the other and the same no-thing happens. Came back to it an hour or so later and got the same no-start.
I hooked up to VIDA and searched for faults. Absolutely no codes in any module. I'm also new to VIDA and don't know much. I may have missed some steps. Seems odd tho that the CEL lights but stores no code.
Absolutely no unusual smells, either from fluids or electrical shorts in the engine compartment. No drips from below. Oil is proper. Coolant is proper.
Disconnected the negative battery lead and waited 10 minutes. Still nothing.
Two bits of info that may be helpful:
1) Transmission valve body was recently replaced prior to my purchase. Could this be the issue? I did shift it into neutral and tried to start it again, and still nothing. Shifting has been good. Really good in manual mode.
2) There has been a prominent buzz that came from the center of the dash, toward the firewall. I could also hear it under the cowl in the engine compartment. It wouldn't be present at initial start-up. It would appear after driving a bit. And it would re-appear right away after I started again from a short shut down. Stayed on til next shut down. Yesterday it came back but disappeared in a few minutes. Today I didn't hear it at all. It sounds like the buzz from an energized relay, or a speaker that has a ground loop. Fairly certain it isn't the center speaker, tho - it shouldn't hum if the radio is off. Wondering if this might be the component that crapped out. I never did pinpoint the source exactly. Maybe the fob dock? I have read these do give out.
Starter relay, maybe? Not sure which cube it is in the fusebox. I read it was #34 (30A), but that seems like just a fuse. It read continuity. And the #27 fuse (5A) in the passenger compartment (START/STOP ENGINE button) is good.
Any thoughts are appreciated.

-ManDude

'79 245 - "The Slovo" Long gone
'80's something 940 wagon - short-lived, long gone
'95 850 - "Junior" Beloved 200k mi+ - RIP 2018
'02 S80 T6 - "Buster" 178k mi - Rough but zesty
'03 XC90 T6 - 148k mi - Jealous of the new car...wants a new home
'10 S80 V8 - 101.5k mi - Hopefully the last car I will ever buy

[Mandude]

Update:
I hope this will help someone.
After my first post, I went back and DID hear the click of the solenoid. Got me to thinking it was the starter. Kept my fingers crossed it wasn't the Starter Control Unit.
I wound up replacing the starter to no avail. Same thing.
Set up an appointment with my indie to test the SCU. $200+ to tow, $285 for the part, a couple hundred more for labor. Glad I watched a little more YouTube before I towed it.
I wish that I would have followed the advice of the wise and had tried every test before buying parts and doing a major install.
Turns out, my no-start condition was the fusible link on the B+ cable from the battery to the starter. I found a YouTube video where a guy jumpered from the + terminal to the starter on a P3 S60 and got it to go. I also found another video where a guy actually showed the continuity fault on the cable at the fuse link on his P3. For now, I have an AutoZone generic cable going to the starter, but I will be upgrading it to the correct part soon.
Do every possible test that doesn't require a part before you do as I did...