Boot Camp install fails: unable to create partition

Not sure what you're saying? There is NO other physical storage connected to the laptop. Just the internal SSD and the thumb drive with the Boot Camp set up.

I appreciate your attempts to help. However:

1. Resetting SMC is not indicated. My impression from reading the link you gave is that it isn't something to be done casually unless certain conditions are present -- none of those conditions are present on my laptop.

2. Same comment re: NVRAM reset.

3. The message I got (twice) is exactly the "we couldn't create a new partition or locate an existing one". There are NO physical drives installed on my MacBook Pro other than the Boot Camp install thumb drive and the internal SSD.

I note your advice to try again using "the last option in BC Assistant". That option requires me to remove the BC partition and then re-install a new BC partition. Is there any way to avoid that sequence i.e. do I have to remove the BC partition and then re-partition the drive?

It appears that BC formats the BC partition with FAT. The Windows installer immediately says the partition should be NTFS. Why does BC use the wrong format? I've seen this before (many times, doing Fusion installs) and re-formatting in the Win installer has always worked. But with this BC install of win 10 that seems to be where the hangup is.

Further to this morning's post:

I have windows 10 working in Boot Camp -- sort of:

reset NVRAM

removed SD card and ANT+ USB dongle

removed and re-partitioned Boot Camp partition using disk utility (formatted FAT)

booted from Boot Camp USB drive using boot selector (alt/option at power up)

Windows installer started (and screen resolution was correct, unlike when booting from boot camp assistant)

had to re-format the BC drive using windows installer

install proceeded normally

However:

Install of Boot Camp drivers using the Apple software has not yet succeeded entirely -- the program hangs at RealTech Audio and won't respond to anything (have to force quit/restart) to get back control. The BC installer is working fine until it gets to REalTech e.g. the wifi drivers are installed and work. Installing REalTech using the package in BC works, too, but the BC installer doesn't recognize that RealTech was already successfully installed and BC hangs.

Will try to re-download the BC software package again and see if that works. But the basic Windows 10 install is there now and works, it just doesn't have all of the Apple package drivers yet.

Thanks. I'd already found the thread about the RealTech hang -- the workaround worked for me. The Win10/BC install now seems to work fine, wifi, trackpad, etc.

Appreciate your help, thank you again.

PS The SD card is my timeline backup and, although it's in plain sight, I forget that it's an 'external device'.

PPS Although I've done many Windows/Mac installs, I hadn't used Boot Camp for a few years (all Parallels or Fusion). I learned a lot doing this one! IMO Apple does a lousy job with BC. I know, they say: "we don't support this". I'm a loyal Apple customer of 30+ years; how about support the CUSTOMER?!