@Chas123
I reviewed your post and I understand that you are unable to print and all the lights on the printer are blinking.
Don’t worry, I assure you I will try my best to get this sorted.
I recommend you follow the steps in the below article and check if it helps.
https://support.hp.com/us-en/product/hp-envy-pro-6400-all-in-one-printer-series/29256678/document/c0...
Let me know how it goes and you have a great day!
P.S: Welcome to the HP Support Community 😊
If you wish to show appreciation for my efforts, mark my post as Accept as Solution. Your feedback counts!
Cheers!
Stay Home – Stay Safe
The_Fossette
I am an HP Employee