Error With Cart, Blank Pages, Offline Site After Clear Cache And Force

[FELINA]

Hello,

In my site ATODAFIESTA.com I cleared cache and forced compile and I am getting this message each time someone tries to buy a producto:

"Impossible to add the product to the cart.
textStatus: 'error'
errorThrown: 'Internal Server Error'
responseText:"

when trying to add an item to the cart and cart pages as well as some back office pages are coming up blank. And also sometimes this error appers: ERR_CONNECTION_TIMED_OUT

 

The site was working yesterday. 

 

Anyone have any suggestions or experience with this?