HP LaserJet Enterprise 600 Printer M603 series - Manual (Page 203)

3. Make sure that the paper is flat in the tray at
all four corners and below the maximum-height
indicators.
4. Slide the tray into the product.
5. Press the OK button to clear the jam message.
6. If a jam message persists, a sheet is still
jammed in the product. Look for the jam in
another location.
Clear jams from the optional 1,500-sheet tray
1. Open the front door of the tray.
ENWW Clear jams 187