CoQueLiCot

Hi everyone! Player from Berlin, Germany here. Just bought a Variax 500 on Ebay from a shop. By the serial number I guess it´s 20 y old but it looks absolutely brand new, even the protective foil was still on the backplate. There´s not a scratch or mark on it. All electronics - after spending about an hour with it - work perfectly. Except ... there´s no sound from the 3rd (GH-) string. The shop says it was fully functional when shipped (Shop is here in Germany) and it even went to a guitar technician a few months ago for inspection. I´ve already read some similar posts on this forum and I had a good luck at the saddles, but there´s is no visible dust or dirt on the bridge. Also the tiny black wire on the 3rd saddle seems exactly like the other ones. I noticed the saddles cannot be height-adjusted, so I just moved it a bit to see if there is a contact issue. Nope. But still no sound there. So I´m asking how do get a support ticket and/or tips on where it can be repaired?