Complete / “finish course” button missing

Hi,

I have developed an e learning platform and in some cases, as the one I have attached thorugh the link, “Complete” and “finish Course” buttons lack. They are not shown at the bottom of the page.

Why does this happen? Has this negative consequences on the students activity?

Given that I have purchased the Certifcates plug in, there would it be some problems in the certificate delivery, if the “finish course” button does not appears?

Yours faithfully,
Luca

The page I need help with: [log in to see the link]