Table of Contents not generating?

Version: 25.8.3.2 (X86_64)
Build ID: 8ca8d55c161d602844f5428fa4b58097424e324e
CPU threads: 4; OS: Windows 10 X86_64 (build 19044); UI render: Skia/Raster; VCL: win
Locale: en-NZ (en_NZ); UI: en-GB
Calc: CL threaded

I have just gone through a small collection of song lyrics and meticulously applied “Heading 1” to each title line. Then at the top of the document, I inserted a Table of Contents. The screenshot shows what I got. What am I doing wrong?

Please attach a sample file, reduce the size as much as possible without private information.