Members of the Aslef train drivers' union had met with the train company yesterday for a second day of talks at conciliation service Acas, but they ended without resolution.
So today's another day of travel disruption for the 300,000 passengers affected, with Southern cancelling all of its 2,242 weekday services.
It comes after a group of fed-up commuters banded together to protest outside the Department of Transport (DfT), seeking "immediate intervention" by the DfT into the industrial dispute, and an independent public inquiry "into collapse of Southern rail". If it fails to do so, the pressure group is calling for transport secretary Chris Grayling tp resign.
The group said it was seeing "nothing but inflammatory and 'politically motivated' statements from the transport minister".
Grayling had previously called the strikes "politically motivated" and designed to "create maximum disruption".
The tense dispute concerns driver-only operated trains, with the unions saying they are unsafe, while the company says such trains already run across the rail network.
The RMT union has also been staging its own strikes over a series of months.
Nick Brown, chief operating officer, of Govia Thameslink Railway, Southern's parent company, said: "We're deeply disappointed, as our passengers will be, that Aslef has been unable to accept our proposals and that we cannot find a way forward to end this dispute with the drivers' union at this stage."
The company had put an offer on the table for the union to consider in an effort to get today's strike called off, but said the union "will not shift from their entrenched position".
Brown added: "Passengers and businesses are being held to ransom by the unions' wholly unjustified and unnecessary industrial action."
An Aslef spokesman said the union hadn't expected a resolution yesterday and that it would meet Southern again next week.