The default format is always FAT and I have no reason to change it as both Win and OpenBSD can handle it.
I've never seen any OS fail to "see" the card/disk/USB stick, whatever, no matter what the format is. They usually report that it is not formatted or some such.
I'm glad both OSes are on the one computer so that I know the H/W works and the problem is with windows or maybe the driver sucks.
Entered all the model/type/subtype etc data.
Showed up a driver for the Ricoh SD/MMC device.
Downloaded, followed the README, installed without complaint. Mandatory reboot.
The device page still shows missing driver.
It's over 50 years since I joined IBM as an engineer and I'm sure that some software (I'm looking at you Microsoft!) gets worse as the years go by.....
I eventually called Lenovo (after thinking that I needed to wait until daylight - they are online for Australia 24/7) and they had a first guess that was my first guess - the device driver. When advised that I had installed the same one they suggested a BIOS update.
We did that but it wasn't an instant answer - the device driver had to be re-installed.
All is well.
Thanks to those who answered & hope this clue finds others with a non-working sd/mmc card.