China may have held back a response because they don't need or care about Maduro. They want influence and access to Venezuela. The China friendly Venezuelan government is still in charge. In the absence of any further US action in Venezuela or US persuasion of the remaining government (which I think must happen), China still has access to Venezuela without Maduro.
Ultimately, it's certainly possible that China may not act because of its pending Taiwan plans. My point is that it hasn't responded yet to the US action in Venezuela because for China's objectives, nothing yet had changed.