MS Word field code error - "Error! No text of specified style in document"

I just opened a word document, in MS Word 2007, and the following error appears before the Figure and Table numbers:

Error! No text of specified style in document

The figure/table names code (after pressing alt-F9) looks like:

Table {STYLEREF 1\s},{SEQ Table\* ARABIC\s 1}

This error was not present when I worked on the file previously and I am the sole user of the file.

Why is this error occuring and what is the best way to troubleshoot/solve this problem?

{ STYLEREF 1 } is looking for a paragraph with the built-in style "Heading 1" (in English language versions of Word - if you are using another language version the heading styles may be named differently).

So if you don't have one of those, the { STYLEREF } field will flag the error you are seeing.

One other way to fix this is to insert a Heading 1 formatted line as hidden text. The error will disappear. I used "Hidden heading 1" so I would remember why it was there. Works on Word 2016.