The solubility of sodium acetate is interesting (that means confusing!). Sodium acetate exists in two forms: anhydrous and trihydrate. When compounds exist in two forms like this, the solubilities, given in grams per 100 mL H20, are predictable: the hydrated form is much more soluble, because it is only partially the compound, and the other part is extra water, the solvent.
However, sodium acetate displays a different behavior:
Sometimes different hydration stages of compounds have different temperature ranges of stability and solubility, but the behavior of sodium acetate is unique. The precipitate that forms so impressively upon cooling is probably the trihydrate, because the amount of sodium acetate in solution according to the recipe does not seem (in my quick estimate) to exceed the solubility of the anhydrous compound, and so the solution produced might be metastable. For some length of time. But, we may be able to initiate crystallization by scratching the glass container, or stirring it, or allowing a drop to dry completely to produce some solid, then using that as a seed for the rest of the solution. Or freezing it.
What I have done is to heat some (pure) sodium acetate to form a concentrated solution (calculated to be supersaturated at room temp), then cooled it: no ppt. Then I touched the surface of the solution with my fingertip and BOOM! Crystallization proceeded like a shot, producing a mass of crystals that filled the container and solidified the former liquid mass. (Did I say it was supersaturated?) I was surprised at the mass of crystals compared to the amount of material I had added to the water at the beginning, but did not think about it till now.
It turns out that the solubility curves of trihydrate and anhydrous sodium acetate are quite separated:
The formation of trihydrate at low temperatures must be a difficult process, and the brown goo obtained here might signify some crystallization inhibitor is present. Maybe a slight excess of NaHCO3 or HCH3CO2 is holding things up - you could try adding a drop of the vinegar, or a few grains of NaHCO3 to see if that changed anything. But If you have a glass rod, scratch the side of the glass container - that works almost all the time.