Students can’t access courses

Hi,
I’m having some issues with my website. When my students buy a course and I upload it to be completed, they can’t access to the curriculum with their account. It’s been happening for a long time and I need to solve this so my website can work as it should be. Is not happening to all of them, just a few, but it’s hard to work this way. We’ve just update the new version of this plugin to check if it solves it. But can you check with us what could it be happening?

Can you help us?

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