You might check some internal settings, scan hardware setup, and examine the situation from every possible angle.
It includes if your USB Flash is perfectly attached to the system or not.
When you face such a situation where USB won't show up on Mac, you must check all your connections first. Symptoms of Mac not recognizing USB Drive So let's have a look at all the signs that indicate that your MacBook Pro not recognizing USB drive. While the reasons could be many, but first, it is essential that you rightly assess the situation. But when you plug it in, your Mac doesn't recognize USB. You might have come across a situation where your friend has sent you photos on a Flash drive. Part 1: Why Mac doesn't recognize the USB drive
