@Sharon119 

Yikes!  That's shocking that you cannot use a slash in the name of a product.  This must be new.  There must be many thousands of customers that use QB Online for 1/4" hose, lines, sockets, etc. that are going to be upset.  

@JustinDaveC 

"Considering you've already exhausted all troubleshooting options but still without success, I recommend reaching out to our QuickBooks Online Support Team. They can investigate the root cause of this issue and recommend necessary actions."

Your colleague already told your customer that they're out of luck.  A slash in an unacceptable character for a product in QBO.  What is your Online Support Team going to be able to help them with?