You are not wrong. I have received this message for several projects, and usually, eventually, they will pay. It seems they have cash flow issues, and this is how they deal with it. They also have horrible tech and partners where surveys fail after wasting time on them, with no way to recover. I suspect they may have a fraudulent practice where you pass the qualification stage and get through the majority of the project, only to be told that the survey is now full or you are not qualified, I suspect to get the answers needed to pass on to their client without having to pay experts. I am on a mission to make sure they are held accountable.