Hello, @Manuel Rivas,
I have debugged your site and found this error in your site console when trying to access the cart and checkout under theme options: https://postimg.cc/v1hzkfFC and that is the main cause of the issue, you can check the error file path as well in the given screenshot, It is coming from the WordPress core files, so it look likes you have added some Custom Code in Core files of the WordPress, Please try to contact your developer to check it for you or contact your hosting provider on this issue, once that issue in console with the WordPress files will be resolved, The option of the theme will work fine automatically.
Regards 8Themes Team.