AIUI, and i'm no expert, it would have to be absolutely massive. When someone put up a banner and burned some tires in Beijing the other day the CCP was blocking the word "beijing" itself on social media for a time. Their level of control is unrivaled.
Is that evidence of awesome control or lack of it? Seems like blocking a word like Beijing because of a single event is over-blocking on a staggering scale; it communicates absolute terror of the populace that results in astonishingly over the top decisions.
You really have to define successful. Get Xi to change a single policy? Get someone else to take over as Chairman of the CCP and Secretary General of the Politburo? Put a democracy in place?
Those are all different goals. Similarly, and as an analog, concerning Russia some people talk about Russia pulling out of Ukraine, some people talk about a coup deposing Putin and some people talk about new, real, elections.
Also, "revolt" doesn't have to mean "completely overthrowing the government". Social unrest can eg. make for a less-cohesive society, harder-to-govern citizens, less-effective economy, etc. These things are valuable to those in charge; a leader would have to be really dumb to not factor them in at all in their calculations. So it's all about tradeoffs: what it would take to appease people vs what would be the social costs if you don't. Finally- protests signal to fellow citizens too, not just the people in charge. They can be contagious.
All of which is just to say their impact is never zero, even if it's small
