HP LaserJet Enterprise M4555 MFP series - Manual (Page 297)

Clear paper jams in the stapler (for models with a stapler/stacker)
1. Press the release latch, and then slide the
stapler/stacker away from the product.
2. If jammed paper is visible, pull it straight out.
3. Slide the stapler/stacker toward the product
until it latches in place.
ENWW Paper feeds incorrectly or becomes jammed 277