In order to answer that, I have to come back to your earlier question and throw in my two cents on it.
Sanctions as a strategy make sense if they're aligned towards a reasonable and a feasible objective. I think the reason we're all sitting here saying that sanctions aren't working is that the objective that has always been outlined for the sanctions is the denuclearization of North Korea. I don't believe that is a realistic objective so long as the regime in North Korea has the character that it currently has.
Partly, it's not the fault of sanctions that we can't make it happen, in my mind. That's not to say that sanctions are not useful tools in meeting other objectives short of that—in my view—quite lofty goal. For example, there might be a chance that sanctions change North Korea's cost-benefit calculation to come to the negotiating table and negotiate something that looks like nuclear restraint. That cost-benefit calculation is probably different for them from what it is for denuclearization. Similarly, sanctions are there as well to prevent North Korea from proliferating dangerous technology to others. That's an objective that's feasible and is worth maintaining sanctions for.
To come back to your question on China specifically, I still need to be convinced that if China were to implement even the sanctions it has already agreed to in the UN Security Council, doing so would sufficiently change a cost-benefit calculation in Kim Jong-un's mind to make him say that he's ready to give it all up. I'm doubtful that this is a calculation we can affect, even if China were to co-operate on it.
In terms of other objectives, I think Chinese participation would be more significant, for example, on such objectives as preventing proliferation to others or changing North Korean calculations over the merits of nuclear restraint and responsible nuclear behaviour. That's a separate discussion that I think is really worth thinking through in more depth, rather than just using the standard narrative that has become so mainstream now, which is that sanctions don't work.