Repeat header row at the top of each page does not work as expected...

To be a repeating header row, the row must be the first row of the table (multiple rows can be selected, but they must include the first and be contiguous. (Make sure, however, that you don't have the entire table selected when you designate a row as the header row.)

In addition, the table must have text wrapping set to None (Tabletab of Table Properties).

If the table contains a manual page break, the header will not repeat. You can, however, insert a page break without breaking the table by formatting a row as "Page break before" (on the Line and Page Breaks tab of the Paragraph dialog).

Note that this applies only to tables. If you want a page header, you need to add a header to the page itself.