As in, the February and October Revolutions still happen, but the latter (which is what I think most people, certainly myself included, think when we hear 'Russian Revolution') fails? IMO the most likely development is that Russia's weak republican government totters on for a while longer, perhaps buys itself a full decade if it sticks around to see WW1 to the end and makes commensurate territorial gains at the peace treaty. But if the Great Depression still happens - and it probably will, because I can't think of any reason the Soviet Union or lack thereof would affect American stock speculation - this government will be easily toppled in a military coup, after which you'd see said coup's leader (perhaps a longer-lived Lavr Kornilov, or if not him then another conservative general like Anton Denikin) seize power.
If the October Revolution fails/never happens due to the republican gov't bailing on WW1 in the spring or summer of 1917, the above coup would probably arrive much sooner, as the Provisional Government now suffers the stigma of having made a Brest-Litovsk style peace and it can't count on the Entente's help in patching their economy up later. Either way, Alexander Kerensky doesn't strike me as a particularly competent, bold and resourceful leader of the sort that would be needed to stabilize Russian democracy and resuscitate the economy.
Not sure what would happen next. Maybe the conservative junta endures as-is. Maybe they'd restore the Romanovs as their puppet: Nicholas II is too tainted to be given back the throne, but I could imagine Denikin or even Kornilov (despite the anti-monarchic sentiments the latter had developed by 1917) making the pitch to Nicholas' son Alexei (if he's still alive, he's a hemophiliac after all) or another Romanov relative to boost their regime's legitimacy. Or maybe the military dictator won't be able to convince the Russian people and the entire army to obey him, and the country will descend into a period of warlordism.
Also, without the Soviets around as the great Communist boogeyman and supporter of further Communist uprisings in Europe (I'm mainly thinking of the failed Hungarian and German ones) the Nazis might well find it much harder to ascend over the democratic Weimar gov't in Germany. The post-WW1 settlement in Central and Eastern Europe would endure for much longer if that's the case, or perhaps their place might be taken by a revanchist but less genocidally psychotic militarist regime putsching the Weimarites instead. If the latter emerges in the same timeline as a Provisional Gov't that survives by making an alt-Brest-Litovsk treaty with Germany in 1917 (and also gets taken out by a military coup in the '20s), ironically we might end up seeing a Russo-German rapproachment and alliance against the post-war order being upheld by the remaining 2/3 of the Entente and all those newly independent states between Russia & Germany (Poland, Ukraine, the Baltics, etc.)