The POD is essentially the prevention of the Bolshevik seizure of power in October 1917. Let's say Lenin doesn't make the train, or is arrested ect. Point is Lenin's party isn't going to be seizing power any time soon.
The constituent assembly, from what I remember probably happens as per the OTL schedule. (If I'm wrong about this I apologize.) And as per OTL, the Socialist Revolutionary Party wins a majority of deputies. However in this timeline the Bolshevik's are not in a position to prevent the members of the Socialist Revolutionary Party from forming a government. Instead of Lenin's government we see a government presumably headed by Victor Chernov if the results of that election resemble OTL patterns.
So what happens to Russia under these circumstances?