Use Header Names as Labels is not working

Lots to unpack there...

For a start, I assume you're talking about Numbers, the spreadsheet app... that isn't clear.

When you say it 'is not working', do you mean:

You enter a header name and it throws an error?

You enter a header name and it picks some completely different reference?

You enter a header name and it reverts to classic A1-style references?

Something else?

That's all assuming that :

a) you have header names as labels turned on in preferences

b) you have unique header names in your table(s) (the feature doesn't work if headers are not unique)

c) your table has 1 header row and 1 header column (things can get confusing if you have multiple header rows/columns - doable, but confusing)

If all the the above assumptions are true, more detail is needed.