Plugin needs update but no option to upgrade the free version

Hello there, 

Please suggest how to resolve the issue its inturrupting the site performance.

The issue is that for the last 10 days I am shown that automatic updates are being done, but no update is being done (screenshot attached ).?

I also tried to download the free version but it shows an error (please see the attached screenshot).?

Please suggest how to update the free version of this plugin when i have premium version installed in the plugins section (I don’t want to lose the vouchers saved in the plugin).

Please suggest

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