Your bootable USB drive could not be created

Hello

I have watched all youtube videos and read as much I found but I'm not able to solve the problem.
I trie to instal W10 to my Imac 27 retina, MacOS High Sierra version 10.13.4, Bootcamp version 6.1.0.

Bootcamp gives me two different errors:
1. An error occurred while formatting the disk.
Or if I try second time then:
2. An error occurred while copying the Windows installation files.

What i have tested:
1. Many different USB sticks (8GB, 16GB, 64GB, all usb3 fast ones)
2. Downloaded different windows files from microsoft webpage (W10 1803, W10 1607, W8.1). I have unmounted iso files, I have created new image (DVD/CD master) and renamed it ISO.
3. ISO file locates on internal drive.
4. I downgrade my mac to Sierra because I have installed windows to macs where was Sierra and i didn't have any problems. Now I'm back to High Sierra.

I'm starting to think that there is something to do with this that I changed 1TB HDD to 1TB SSD. At first in my imac was fusion drive. At the moment i have two different drives, 1TB SSD and 24GB SSD (not used).

Probably it is small stupid thing what I do wrong but I have lost so many hours and days, I would be really thankful if someone can help me 🙂. Thank You !