Signature list page navigation problem

Hi,
my signature list has about 6000 signatures. I present it in reverse order on my page, but I can’t navigate backward. The “>” sign is presented on the bottom, but pressing it reloads the page with the same content.
What is the case ?
You can see the problem here:

Thanks for help.

https://www.ads-software.com/plugins/speakup-email-petitions/