Okay, have you checked if ML is switched on in the BL3500?
Press MENU MENU 0 9 GO then use the up/down arrows to make sure ML-ON is selected. Once selected, power down the BL3500 and remove the mains for a few seconds then re-connect.
(If your BL3500 is an early SW version, you may only need to press MENU once).
If that doesn’t work, check the serial number of your BL3500? If it’s lower than 10552474 then pins 4 and 12 must be short circuited in the ML socket of the BL3500.)
