nextpage not working

Sorry, forgot to add this question to my other post.
I should first mention that i have the latest updates of WO core auto-installed and that i tried a ton of different themes before Tempera, some equaly modern, some older. I also tried this on different hosting accounts – always with the same result –
<!--nextpage--> is NOT working.
Tempera’s single.php has php wp_link_pages built in so it should work just fine, but it does not, checked in Chrome and SeaMonkey.
Asked already at the WP main forum, not resolved, they instead told me to ask here, all though i told them i tried plenty of other themes and hostings and it did not work in any anywhere ever – anyone in the knowing what is happening with this nextpage thing??