Why is the blue wireless light on my HP OfficeJet Pro 8720 blinking or not lit?
If the blue light on the printer control panel is not lit, wireless may be turned off. If the blue light is blinking, the printer is not connected to a network. Use the Wireless Setup Wizard to make a wireless connection.
From the official HP Officejet Pro 8720 All-in-One Printer manual, page 3
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