Fixing HP Printer 14 No EP Cart Error Message

“I have an HP LaserJet 4 printer with the error message 14 No EP Cart . I recently replaced the ink cartridge, ran ‘self test’ on the printer, now the message 14 No EP Cart won’t go away. The printer will not print. Help.”
There are several possible causes for the 14 No EP Cart error message that vary by HP printer model. For HP LaserJet 4 series printers, the likely cause is one of three things: