Gelling is a sign of collagen’s presence but it is not required for collagen to be present.
Many people who make their own bone broth use the sign of the bone broth gelling to indicate that they have collagen in their broth. This is useful when you don’t have access to a lab to analyze your broth. However, just because your broth might not be gelling, doesn’t mean that there is no collagen present.
Here is a great article that will give you more detail about the difference between gelatin and collagen. The Benefits of Gelatin vs Collagen.