Cannot partition SSD in Bootcamp or Disk Utility

Many users have posted problems similar to yours. In every case, APFS in involved.

Below are the instructions for installing Windows 10.

Note: To get a better view of the images shown below, either click on an image or open an image in a new window.

1. (In your case, you can skip this step.) Remove all Windows related partitions that may have been created by previous attempts to install Windows. When finished, the output from the command diskutil list disk0 should appear similar to what is shown below. Other users should assume their sizes will be different.

   /dev/disk0 (internal, physical):
      #:                       TYPE NAME                    SIZE       IDENTIFIER
      0:      GUID_partition_scheme                        *500.3 GB   disk0
      1:                        EFI EFI                     209.7 MB   disk0s1
      2:                 Apple_APFS Container disk1         500.1 GB   disk0s2
   

2. The command below will create the 150 GB "BOOTCAMP" partition on your internal drive. If you want a different size, then make the appropriate subsitutions. The space occupied by this partition will be used for installing Windows.

   Note: The two sizes given in the command below need to equal the size of your disk0s2. In other words, 350.1 + 150 = 500.1.

   sudo  diskutil  apfs  resizeContainer  disk0s2  350.1G  FAT32  BOOTCAMP  150G
   

3. Use the Disk Utility application to erase a 16 GB or larger USB flash drive. Enter the settings shown below in the popup window. When finished, do not remove the flash drive.

   

4. Use the Boot Camp Assistant to download the Window Support Software. Look for the "Action" pulldown on the Boot Camp Assistant menu bar. On my Mac, these files were downloaded to the ~/WindowsSupport directory.

   Note: You can not download the Boot Camp Support Software for your Mac computer from any Apple website. You must use the Boot Camp Assistant to download an officially copy of this software.

5. Mount the Windows iso file and copy the contents to the "WINSTALL" volume. You will need the use the cp command from a Terminal application window. Below is the exact command I usually use. The string ESD-ISO is the name of the mounted ISO file from Microsoft. If necessary, make the appropriate modifications.

   cp  -Rv  /volumes/ESD-ISO/  /volumes/WINSTALL
   

   Note: This command will take a while to complete. Be patient!

6. Copy the Windows Support Software to the "WINSTALL" volume. Below is the exact command I usually use. If necessary, make the appropriate modifications.

   cp  -Rv  ~/WindowsSupport/  /volumes/WINSTALL
   

7. Continue starting at step 3 of my answer to the question Boot Camp Assistance is stuck on create a partition?