Ryan
Based on this response I guess you had a HAL and the Surface Model and you wanted to plot Cross Sections - so you created the Corridor and then did not add any instructions to the Template - if you had added this surface that you referenced as a Surface Instruction you would have got the same result - however you can of course also do it this way.
Typically the Reference Surfaces are used to display "Additional" surfaces in the Corridor Template Editor - e.g. Existing Ground, Strata Layers etc. and the Template Instructions create the Finished Grade, Subgrade Layers etc for the Design Model.
Adding a Reference Surface basically tells the Corridor Model to slice the surfaces listed and checked at whatever station is being displayed in the Template Editor - the displayed surface slices are termed "Surface Cross Sections" and have properties etc that you can review if you click on the line in the Template Editor.
Because the Corridor has "Sliced Reference Surfaces" they can be plotted using Cross Sections, however a reference Surface cannot be directly used to give Cut / Fill Volumes or Sectional Areas - for that they need to be added as a Surface Instruction in the Template.
Hope this helps
Great to have you on the Community and in the TBC Power Users Group - Welcome ....
Alan