@ericonline
AddColumns, RemoveColumns, and ShowColumns are all "chain" formulas. In other words, they *return* the results of the actions that they take, they don't alter the paramters given.
So, in this case, the AddColumns is working, but it is going nowhere.
Typically I would user Add/Remove/Show at the point that I gather the information and assign it to a collection if needed, but in this case the only thing you're going to need is to put this result in a collection.
So - wrap this formula you have with a ClearCollect(colCustomConectorResponse, AddColumns....<the rest of your formula>...)
This will put the results of the AddColumns into the collection.
Also, since you are actually doing this "Post Collection", you might want to designate another collection name as PowerApps might get a little freaky about the change of structure.
Again, it is better if you can, to use the AddColumns at the point in which you initially create your colCustomConnectorResponse collection.
Hope that makes sense.