sliders don't show and update theme to 3.8 fails

Dear Sir/madam,

I have installed the theme Enfold on my WordPress website version 4.6.1.
The layer sliders worked before, I don’t know what happened, but when I add images to a slider on a page, the sliders don’t show. Not in Explorer and nog in Chrome. I tried several types. But no sliders or images show at the top of my website.

So I thought, maybe the theme needs an update.
I see the message that a new version is there and when I try to update the theme, I got the following message:

Thema Enfold (1/1) updating
Downloaden update of https://s3.amazonaws.com/marketplace-downloads.envato.com/files/204665624/enfold.zip?AWSAccessKeyId=AKIAJYG5ROGJ6X7Z3M6Q&Expires=1475830012&Signature=nf6NUNnGtjxcHnFRMCrGV6nvUhA%3D&response-content-disposition=attachment%3B+filename%3Dthemeforest-4519990-enfold-responsive-multipurpose-theme-wordpress-theme.zip…
An error occurred while updating Enfold: Download failed. Forbidden.

Can you let me know if there is a possible solution?

Kind regards,
Sandra