Both my 2010 MacBook and my 2015 MacBook are running 10.13.3. My USB stick works fine on my 2010 MacBook. But on my 2015 MacBook it won't mount on the desktop, so I can't access the files it contains. However, it can be seen on Disk Utility, and when I run Disk First Aid, it says it is fine. (The USB worked with 10.13.2 on the MacBook 2015, although occasionally it needed to be inserted again. ) The USB Stick is MAC OS Extended, journaled. Is there anything I can do?