What is the first question to ask customers who call HP Support reporting that their HP Color
LaserJet Enterprise CP4020/CP4520 Series Printer or CM4540 MFP front door does not close?

A.
Is the toner collection unit (TCU) installed?

B.
Are all four print cartridges installed in the correct slots?

C.
Are the Protective Glass Cleaners (PGCs) in the correct alignment?

D.
Is there currently a paper jam in the Tray 2 pickup area?

Explanation:

Reference:
http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01860406/c01860406.pdf (page 164)