MP 7,1 Bootcamp partition not starting up. Win 10Pro on 7,1.

[H2SO4]

Hi all. Suddenly started having problems booting Windows. (The only thing I have done since the last boot is to upgrade to 14.5).

So I shut down and then option boot to start up and my Mac OS internal drive and BC partition appear.
I choose Windows and the screen momentarily goes black as normal. Then a 5-10 second pause and the Apple logo reappears followed by a screen that only gives me the option of Start up disk or Recovery assistant.

Since the first two refusals to boot, I have gone through a safe boot on the Sonoma side just to makle sure that is cool and also pulled the power cable for 30s.

Anybody seen/heard anything like this at all?

FYI, Windows is on a Sabrent Rocket 4 Plus 2TB NVME riding a Startech adpator, (https://www.amazon.co.uk/dp/B081SJYCTL?psc=1&ref=ppx_yo2ov_dt_b_product_details). Disk Utility calls it, Sabrent SB-RKT4P-2TB Media.
Mac OS is on the original internal drive.

Thanks.

 

[H2SO4]

Hi all, replied to myself just in case anybody else gets in this situation.
Schoolboy error on my part.
It appears that if you have anything except 'no security' set in your start up utility options, Mac OS doesn't even consider Windows as a trusted OS.