Liquidity Requirements

We're looking for a co-op on UES. We've run into the issue of putting in very solid offers (offer ask, etc.) where we would have more than 2 years of mortgage/maintenance costs available in post closing liquid(non-retirement) assets, only to be told we weren't considered "financially strong" enough by sellers to take to their board. How do we find this out up front so we stop wasting our time with apartments we think we can clearly afford? Or is this just a proxy by a seller that they don't like something else about us? Listing sheets always indicate what board will allow you to finance, and yet there's no info on post close liquidity requirements??