Unable to format USB flash I am trying to format my USB flash in ExFAT format to make it work on both Mac and Win devices. But I am unable to format my USB flash because I am getting an error when trying to format it via diskutil.

1) Check our external device in disks list:


2) Format:


According to the internet answers, I have tried to boot in safe mode and format USB flash then - but also got 'could not open device' error.

Can somebody help me with this?

P.S. Result of execution command from the question comment:
Macs cannot format NTFS drives because they can only read NTFS formatted drives. But if you badly want to format it to Exfat you could use a windows computer to format it to Exfat or install a third party app to format you NTFS drive.