Yes Means No
A ‘yes’ that is phrased as “It may be possible” or “We’ll check into that,” and so on often really means ‘no’ unless there are extenuating circumstances that will make someone feel obligated to get creative and/or motivated about helping you (e.g., they owe you a favour).
Failure to follow through on a ‘promise’ in China is not necessarily considered insincere. Among themselves, the Chinese have the ability to distinguish between a (polite) ‘yes’ that means ‘no’ and a ‘yes’ that actually means something is going to happen. One clue to the former is an uncomfortable or reluctant attitude on the part of whoever is responding to you; another is a vague response or an awkward silence prior to a reluctant response.
No Means Maybe
On the other hand, the Chinese can give a flat-out ‘no’ as an answer. However, when they say ‘no’ with what seems to be an unreasonable amount of force, it may mean they see barriers to what you have proposed that you do not see or, as a foreigner, do not face yourself. They will not necessarily tell you what those barriers are, but if they exist, their ‘no’ is generally a firm one.
That said, they may also be saying ‘no’ to put you off because they cannot get the proper approvals, cannot be bothered to think through what needs to be done in a relatively complex situation, or simply do not recognise the importance of the request. These are the kind of no’s you can influence, by subtly encouraging your counterparts to push for approvals, pointing out the advantages to them of helping you, etc.
In these situations persistent but patience persuasion is the key to getting the genuine ‘yes’ you want. Flexibility must be (perceived as) two-sided, and sometimes simply agreeing to include a modification for a standard product or an equally straightforward compromise is all that’s required to close the deal.