Here is what they said in hosting support
Included error logging in the PHP_errors.log file, it is located in the public_html directory of your site. Judging by the log, the site does not work due to the following error:
[24-Jan-2019 04:28:47 UTC] PHP Fatal error: Uncaught Error: Call to undefined method WC_Product_Grouped::get_available_variation() in /home/c/charighl/mebel/public_html/wp-content/themes/woodmart/inc/integrations/woocommerce/modules/variation-gallery.php:90
tell me what it is and how to deal with it?