Il ne se connectera pas à l'application même s'il est connecté au Bluetooth

@Molly36, Welcome to HP Support Community!
 
Check if the sprocket is paired in the Bluetooth settings
Update the Sprocket app to the latest version.
 
If the issue persists, you can initiate a factory reset by using the steps below. A factory reset can only be completed when the USB charging cable is NOT connected to the printer.
1. Hold the power button for about 7 seconds in total. After 3 seconds, the Status LED light will turn off to indicate the printer is shutting down; continue to hold the Power button until the LED lights start to flash.
2. Release the power button. The LEDs will continue blinking for about 6 seconds.
3. While the LEDs are blinking, press and release the power button. The device will remain off until you power on again. 4. Power on; the printer will be reset to factoring settings. After a factory reset, all settings are reset to factory defaults (Custom Name, LED color, Sleep Time, Auto-Off, etc.)
 
Hope this helps! Keep me posted. 
 
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