Unfortunately windows can't recognize a partition with this file system on it. Boot into Windows in the Mac's Bootcamp partition. All they need to do is to read the case to see that those questions like 'Have you used a back.
MacOS High Sierra and macOS Mojave upgrade solid-state drives to Apple File System (APFS), which requires to switch between Windows and macOS. If you choose 'Restart in OS X' from the Windows Boot Camp menu, this message might appear: 'Could not locate the OS X boot volume.' Follow these steps to boot into macOS or Windows:.
Restart your Mac, then immediately hold down the Option key. Release the Option key when you see the Startup Manager window. Select your macOS or Windows startup disk, then click the arrow or press Return. Repeat these steps any time you need to switch between operating systems. Information about products not manufactured by Apple, or independent websites not controlled or tested by Apple, is provided without recommendation or endorsement.
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Click to expand.If your High Sierra partition is APFS, then your Mac's behaviour is normal. There is no driver in Windows to read APFS yet. Apple didn't update the Bootcamp software to that level.
Therefore, the Bootcamp control panel cannot display any APFS boot partition. Same reason, that 'reboot back to OSX' won't work either. Apple recommended work around is to use Boot Manager (hold Alt during boot) to go back to MacOS. But if you a more 'software' solution, Bootchamp with SIP disable also work (but you need to keep SIP disabled). Other work around will be like stay at HFS+ (even with SSD, you can clone the OS to another partition, re-format it back to HFS+, and then clone it back). Or install an extra HFS+ 10.12.6 (or onward) to make bootcamp panel able to boot back to MacOS, and then further choose your APFS High Sierra partition inside that MacOS as the next startup disk.
But in general, no one prefer this kind of 'work around'. Click to expand.The EFI partiton almost always there on a modern computer, depends on which OS you are using, it can be 100MB, 200MB, or 300MB in size. It basically use to store the files for booting. For a normal user, my suggestion is don’t even think about to touch it.
If you accidentally damage that partition, change the parameter a bit, or alter the file structure. It can kill your OS which may required re-format the hard drive to make a fresh OS installation. However, if you want to play around with some advance stuff (e.g.
Install Clover, rEFInd, or other boot loader), most likely you will need to access this EFI partiton. In fact, that EFI partiton can be shown in MacOS (e.g. In terminal), just not natively show in disk utility. By running some simple command in terminal, you can mount that EFI partiton, and access it via Finder like any other partition. One of a free simple Mac GUI software call Clover Configuratior can provide easy access of all the EFI partiton. If your High Sierra partition is APFS, then your Mac's behaviour is normal. There is no driver in Windows to read APFS yet.
Apple didn't update the Bootcamp software to that level. Therefore, the Bootcamp control panel cannot display any APFS boot partition. Same reason, that 'reboot back to OSX' won't work either. Apple recommended work around is to use Boot Manager (hold Alt during boot) to go back to MacOS. But if you a more 'software' solution, Bootchamp with SIP disable also work (but you need to keep SIP disabled). Other work around will be like stay at HFS+ (even with SSD, you can clone the OS to another partition, re-format it back to HFS+, and then clone it back).
Or install an extra HFS+ 10.12.6 (or onward) to make bootcamp panel able to boot back to MacOS, and then further choose your APFS High Sierra partition inside that MacOS as the next startup disk. But in general, no one prefer this kind of 'work around'.