Unable to install Windows 10 (Bootcamp) on iMac 2020

[spiritlevel]

I'm having a big problem installing Windows on my new iMac.

Have tried and tried (and so has Apple support) but I am not getting anywhere...

I use Bootcamp assistant to create the Windows partition (200MB on a 1TB internal SSD). I have downloaded the Windows 10 .ISO from Microsoft (twice).

Installing W10 Home, It goes though most of the installation fine, then after a restart I always end up at a error window that says

"Windows could not finish configuring the system. To attempt to resume configuration, restart the computer"|

Restarting just sends me into a loop where I end up at this message every time.

So I tried installing W10 Pro instead. At first it looked a little more promising, then after an auto restart or two I end up with a window that says:

"Why did my PC restart? There's a problem preventing us from getting your PC ready to use but we think an update will get things working again. Here';s how to get the update:
1. Make sure PC is plugged in
2. If PC uses wifi, select and follow instructions to connect
3. If it does not use wifi, insert a network cable to connect to network and click next
4. Once you are connected, click next and the update will install

Here's the thing, I am already connected to a wired network but it seems Windows is not recognising this (on the next window it shows I have a connected ethernet connection, but will not give me a 'Next' button to click when I try and select that.

So I try and connect to my wifi network instead. I select my wifi network, click next, enter my password and then... it restarts, and I end up in another loop where I'm back to "Why did my PC restart" again...

I'm wondering if the problem is that Windows cannot access my internet connection for some reason - even though said connection is fine both wired and wireless when I start up in Mac OS.

Apple support technician took over my computer for over an hour trying to install the Home version and eventually gave up - "I've done everything I can. it's not working. Is there anything else I can do for you today?" Great...

Does anyone have any ideas please? Crazy this is happening on a brand new machine...

 

[allan.nyholm]

Have you turned off(limited) the protection of your T2 chip in your new iMac?

200MB is also too little a partition 200GB would better fit Windows. I knew that you probably meant that.

You ought to be able to install either Windows Home of Pro, but you could have too much security on your Mac.

To the fair I will admit that I've only read about the T2 chip as I don't have issues at all with installing Windows 10 on my iMac from 2015.

About Startup Security Utility on a Mac with the Apple T2 Security Chip - Apple Support

Use Startup Security Utility to make sure that your Mac always starts up from your designated startup disk, and always from a legitimate, trusted operating system.

support.apple.com

"About Secure Boot​

If your Mac includes the Apple T2 Security Chip, you can use Secure Boot to make sure that only a legitimate, trusted operating system loads at startup."

 

[spiritlevel]

Have you turned off(limited) the protection of your T2 chip in your new iMac?

Yes I turned off secure boot (No security) - it needs to be off for Softraid to work properly (my Raid and all USB ports are unplugged when I am trying to install windows).

 

[spiritlevel]

Just an update to say I eventually got this sorted out. It appears FileVault was the problem - after I turned FileVault off Windows installed fine.