Booting from a cloned Windows 10 installation
IMO, flash drives are not designed to endure the amounts of writes that would be performed by having an operating system installed on the drive.
There are many different mechanisms which can be referred to as having cloned. Since you have not explained how you cloned Windows 10, I will assume you are confident Windows 10 was correctly cloned. Windows does have the ability to detect when being cloned and if detected, can result in Windows 10 not booting properly. The general solution to this problem is to rebuild the BCD.

I realize this answer is vague, but this is only do to the lack on details in your question.