It's possible that you'll need to upgrade macOS or switch to a later version of Windows 10.
Boot Camp Assistant may cease responding in certain cases, or it may report that the Boot Camp installation failed when transferring the Windows installation files. To fix the problem, follow these steps:
If Boot Camp Assistant isn't responding, use Option-Command-Escape (Esc) to force the software to shut down.
Install the most recent macOS updates, which may include Boot Camp updates.
Microsoft's website has the most recent version of Windows 10. Then install it using Boot Camp Assistant.
If Boot Camp Assistant states the starting drive can't be partitioned or restored to a single partition, go ahead and do the following:
Open Disk Utility, which is located in your Applications folder's Utilities folder.
In the sidebar, choose your Mac starting disc (Macintosh HD).
Click Partition in the Disk Utility toolbar.
If Disk Utility prompts you to partition the drive or add a volume to the container, choose Partition.
In the graph that displays, click OSXRESERVED, then click the delete button (−) underneath the graph.
In the graph, click BOOTCAMP, then the delete button (–).
The empty partitions OSXRESERVED and BOOTCAMP were created by Boot Camp Assistant during the unsuccessful installation.
To confirm, click Apply, then Partition.
Restart Boot Camp Assistant and try again to install Windows.