Air carrier technician reported finding and documented a hydraulic leak during troubleshooting. They were notified that the discrepancy was signed off as no leak found by another technician.

Narrative

On Day 0 Person A and I were sent on a gate call for this aircraft for yellow system hydraulics needing serviced; we went out and noticed that there was hydraulic fluid all over the belly. We opened the righthand gear door and noticed a large puddle of hydraulic fluid sitting on top of the belly fairing. We then proceeded to run hydraulics and actuate flight controls to try to locate the source of the leak. Nothing was really jumping out but I happen to notice fluid kind of weeping out of the charge accumulator so to verify this I slowly cracked open the Shrader valve and notice fluid seeping from that as well which is an indication of an internal leak of that accumulator. We notified our Crew Chief and took the aircraft out of service. I came back to work on Day 2 and was told the aircraft was signed off with no leaks found. The aircraft made one flight and came back here to [Gate] XX it was getting ready to push off the gate for its next flight when we got a gate call for yellow hydraulics quantity low. Person B went out on the call and I showed him what Person A and I found on Day 0 so he notified our Crew Chief and we took the aircraft out of service again. I then proceeded to follow the aircraft on the web based system and saw that they said they could not find a leak.Cause: if I had to guess it would be due to lack of knowledge of that system on that particular aircraft Suggestions: more training