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error HP
Error Code E7
One or more ink tanks are out of ink. The printer has detected that one or more ink cartridges are empty.
? What Causes This
Ink tank(s) depleted during use.
✓ How to Fix It
Refill the indicated ink tank that is out of ink.
Source: page 15 of the official manual
From the manual
This error code appears in:
HP Smart Tank 6000 Printer