Here is an email snippet I had with a customer this issue.
"Thanks, and you have lived up to your name once again as the shipping process truly was fast! I've got (the Main PCA board) installed and powered up; however, once set the date and time it asks for a USB that came with the printer to install a mandatory update. I don't remember getting a USB when I bought the printer from HP. Do you have any idea for a work around on this?"
. . .
"I've downloaded the firmware from the link provided to a USB, but when inserted into the printer, nothing happens."
. . .
"(HP support) provided nothing of value beyond what I had already found online, and being frustrated to my wits end, I simply started poking around on the front panel screen trying to hit something to get a response. Somehow I hit the magical combination and it said, "would you like to bypass the required update?" I clicked yes, and everything is working now. I've even been able to setup the scanner and scanned a test document to the USB. Unfortunately, I have no idea what combination i entered, but it was tapping several times around the back button, help button, and on the main screen."