MF-102 Ring Modulator stopped working help!

I didn’t use my MF-102 Ring Modulator for 3 years. It was in my pedalboard.
Few days ago I wanted to check it. I turned it on, lights was shining but there was no sound at all.
What happened? What should I do?
16558614_1255877901159758_1873108726_n.jpg

I just got one sent internationally and it’s like this. Lights on no sound. Please, let there be sound.