One Fix When HP All-in-One Printer Prints, But Won't Copy or Scan

My current current all-in-one printer is an HP Officejet Pro 8600 Plus and my previous one was an HP Officejet J6400. Each experienced with scanning and copying, but had no problem with printing. The symptoms were different, but the solution was the same and very easy - clean the glass properly.

The glass may appear to be clean at first glance, but it may be just clouded enough to keep the scanner from aligning properly. The copies and scans I was making just prior to the problem all appeared to be fine.

The symptom with the J6400 was a horrible grinding noise  from the alignment bar. With the 8600, there was no such noise. Instead, I received various error messages, none of which suggested the problem. The messages said things like, "Scan, copy, and fax failed;" and "Can't communicate with printer."

With the J6400, it was the underside of the glass that was dirty. I was very fortunate to find an on-line explanation (by a user, not by HP) on how to access the underside of the glass.

With the 8600, it was the top of the glass that was causing the problem.

There are on-line videos that explain how to clean the glass. It is very important to use glass cleaner or water. It is also important to apply the cleaner to a lint-free cloth, not directly to the glass.