Override the frame on the document page and update the TOC and the entry should show up.
Thank you. I selected the text box that contains the heading on the page master. Selected override master.It still shows up as a blue dotted line when I look at the document...which apparently means it was not overridden.
Sure, you have to override it on the document page (not the master page) in order for InDesign to "see" the content in that frame as belonging to that page (and thus put it in the TOC). For example, if your heading is on page 5, you have to override the frame on page 5 by holding Command+Shift (Mac) or Ctrl+Shift (Windows) and clicking on the frame. The dotted frame will change to a solid frame on that page. Then go to your table of contents page, select the frame containing the TOC and from the Layout menu and choose Update Table of Contents. You'll have to override the frame on every document page where it contains content that you want to appear in the TOC.
That did it.
Have a great weekend!