What should I do if I see error codes Er/07 or Er/11 on the printer display?
Er/07 and Er/11 indicate a cartridge issue, and you need to reinstall the cartridge to resolve them. Refer to the Setup Guide for detailed reinstallation instructions. These codes may flash after initially turning on the printer. (Page 2)
From the official HP Laserjet Mfp M139e M142e Printer manual, page 2
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