I had the same problem back in the summer and put it on the shelf in frustration. Pulled it off the shelf weeks later and then it worked fine. Then today I tried it and it wasnt’ working! It powered up fine and I could hear the faint swishing of the ocillator but no echo. An internet search pointed me in the direction of the power supply which seemed an unlikely culprit to me. My wall wart was a 9V center negative rated at 650mA. However, I had nothing to lose so I switched it with a supply that is recommended for Boss and Ibanez pedals… it is a 9.6V center negative rated for 200mA. Now it works! Switched back the other power supply and bam it stops working. So there you have it. Give it a try.