Help needed: Hydraulic thumb not working on mini excavator (LT1010)

Hello everyone, I recently bought a (new) Chinese mini excavator (LT1010) equipped with a hydraulic thumb. According to the manual, the left pedal controls the auxiliary circuit, but the thumb doesn’t work. Here’s what I’ve checked so far: The auxiliary system is double-acting (two-way), controlled by the left pedal pushed forward or backward. The main hydraulics are fine (the bucket can easily lift the excavator, so system pressure seems good, and the oil level is good). Both shut-off valves on the stick are fully open. When pressing the auxiliary pedal, the engine loads slightly and the hoses vibrate, but the thumb cylinder does not move or just wiggles by a few millimeters. Nothing seems to be physically blocking the thumb movement: i can slightly wiggle the thumb by hand when the machine is off so i don't think the joints are stuck in any way. I tried to loosen the hydraulic fittings directly at the cylinder (quarter turn) → no oil comes out when turning on and activating the circuit with the pedal. I also loosened a fitting at the entry of the shut-off valves (before the cylinder) → still no oil flow. So it looks like the auxiliary circuit is not sending oil to the thumb with enough pressure (or at all?). Has anyone experienced this on a Chinese mini excavator? Could it be that the auxiliary section of the control valve (pedal) is not connected or assembled correctly from the factory? Or a defective cylinder ? Air in the system ? Any advice on what to check next would be greatly appreciated: I have zero experience in mechanics. I'm a complete newbie, so I’m not confident about any of my observations. I'm looking for advice of how to proceed next to better diagnose my issue. Thanks in advance!