Why my hp printer shows offline message

Why my Hp Printer Offline my printer is not connect because it says it is offline. I have tried 4 different laptops, ranging from a Mac, Windows 10 and Windows 7. The printer turns on but despite connecting a USB will not register as 'online'. What do you recommend? We are not sure as we have not needed to print any documents for a long time. It has been at least a year since we have printed anything with it. Hello, every time I want to print from my computer, computer says Printer is offline. I already checked the settings. Only way to get the printer online from my computer, I need to disconnect the printer from the electricity and restart the printer, because I cannot find the on/off button. Printer is always in sleeping mode. I do not have this problem while printing from another device as a tablet or phone. How can I solve this problem on my computer? Visit: HP Deskjet 2540 Offline