steps to reproduce

1. In a workbook with 2 or more sheets, put page number variable on footer (load the attached excel file)
2. export to PDF.

result

Everything is fine in the first sheet. Footer shows "page 1 of 3", for example. But in next sheets, footer shows 0 (zero) as first page -> "page 0 of 2" instead "1 of 2", for example.