Perform an NVRAM reset, clear all print jobs and then try again.
NVRAM Reset for HP Color LaserJet m375/m475:
1. Turn printer off
2. Touch and hold the right arrow and the cancel button
3. Turn the printer on
4. Release the buttons when the message "Permanent Storage Initialization" appears
5. Reconfigure your printer
49 service errors normally mean that there was a bad print job sent to the printer. The printer did not know how to handle the problem and waits for user interaction to clear the job. For us this normally happens when printing PDF documents. We can normally work around that problem by enabling the Print as Image feature from within the PDF settings.
On that note, normally finding the job on the print server and deleting it followed by a reboot of the printer will clear the error message. If your 49 error is appearing on the screen while not connected to anything and rebooting then that means the job has moved onto the local memory of the printer. This is where the NVRAM reset should help to clean up any corruption.