To hard reset the SQ mixer, as explained in the Reference Guide:

 Hold the EQ ‘In’ and ‘HF’ keys when powering on the SQ. This will clear all mix settings and all saved data, including Shows/Scenes and Libraries, so back-up any data you wish to keep using SQ-Drive.

The hard reset:

• Resets all current settings - the same as using the Scenes screen ‘Reset Mix Settings’ button.
• Resets non-scene parameters and user preferences to a factory default.
• Clears scene recall Safes and Filters.
• Clears all memories including Scenes, User Libraries and User Permissions.
• Resets the Network IP address and the touch screen and fader calibration.