Your software vendor is not answering
At one client we asked two parties for structured data. Neither of them sent anything. Here is what we did instead.
At one client we needed data that sat in their invoicing package. Not an exotic request: does an integration exist, an export, a file we can schedule. Any form at all.
No answer came.
Alongside that we asked their wholesaler for an article file, so we could link article numbers to what was lying in the warehouse. Same there: nothing.
That is not an exception. That is simply what happens when an SME asks something of a party with no commercial interest in answering.
Why it goes that way
A software vendor earns nothing on your export. Worse: a client who can easily take their data with them is a client who leaves more easily. That is rarely a stated strategy, but it does explain why such requests end up at the bottom of the pile.
At a wholesaler it is different but just as stubborn. There it is not unwillingness, it is that nobody feels addressed. Your question reaches a salesperson who passes it to someone who passes it on, and somewhere along the way it stops.
In both cases you are left with the same thing: your project hangs on someone who does not call back.
What not to do
Keep waiting. That is the reflex, because it feels like it could come in at any moment and it would be so much simpler.
But a project standing still on an answer that never comes loses its momentum. The owner who was enthusiastic is no longer enthusiastic after two months. And in those two months you have learned nothing.
Put a deadline on it. What we use now: one request, one reminder, and then we assume the answer is no. That sounds harsh and it is simply realistic.
What we did instead
We made it ourselves. Both of them.
That is not as heroic as it sounds, because the question every time is: which part of what I asked for do I actually need, and can I get that by another route?
For data the package does put out in some other form, even if it is not the form you wanted, there is usually a way. A system with no integration often does produce documents. A system with no export can often send something.
And for reference data like an article file: that is finite work. It feels unjust to build up yourself what the other party could simply have sent over, but it is a few days and after that it is yours. With the added benefit that you maintain it in the form you need, instead of depending on how they deliver it.
What you get that you did not ask for
Independence, and that is worth more than it sounds.
An integration you get from a third party can change without you knowing. It can start costing money. It can disappear if you switch packages.
What you build yourself stays yours. At the client in question that data now sits in their own database. If they ever switch invoicing packages, their history stays put and only the feed needs adjusting.
That was not a goal beforehand. It was a consequence of not being able to wait.
The honest caveat
This is not always the right choice.
If the data you are missing is the heart of your project and reproducing it takes months, then building it yourself is not a solution but a delay. Then the conversation with your vendor is the project, and you have to take it higher in the organization or accept that it will not happen.
The distinction: can you make progress with a part of it? Then do that and keep asking for the rest. Can you not start without the whole thing? Then waiting is not weakness but reality, and you should say so to your client in those terms.
The claim
Assume you will get no answer and plan your project so you can start anyway. Anyone who makes their timeline depend on the goodwill of a third party has handed it to someone who earns nothing from it.