Add a "model" step to your pipeline
[edit] i was typing quickly on a call
I see this when the table in question doesn't have an associated model step. In the table, add a model step, and that should allow the columns to show... that being said, it's not always healthy for the project to have a model step leading to nowhere, but it will get you over this particular hurdle
again, appreciate your patience as I typed my answer wayy too fast.