Try this:
"Workaround:You have to activate detect muxes and add a mux manually. The other will be detected automatically.
use the bellow settings
"frequency": 11953500,
"symbol_rate": 27500000,
"fec": "3/4",
"polarisation": "Horizontal",
"modulation": "QPSK",
"delivery_system": "SYS_DVBS",