Double check the filament path getting to the extruder is not binding by checking it’s free of tight bends etc.
If your still seeing the issue, double check the filament tensioner gear retaining pin has not slipped, some have had this issue on the Sovol Zero. Ref: Sovol Zero – under-extrusion caused by worn extruder gear (Solution update - loose pin)? Need advice on replacement
Cheers,
-Mike