If you set some dates as holiday either casual holidays or national holidays in plugin’s holiday settings page, then “Add to Cart” button will be hidden for those dates, it is an inbuilt function of the plugin, as in general no order should be processed/accepted on store holidays, but in your case if you want to accept orders on holidays too..

then go to ByConsoleWooODT.php file and find for this line as

add_action('init','byconsolewooodt_store_closed_remove_addtocart');

and changed this to below

//add_action('init','byconsolewooodt_store_closed_remove_addtocart');

and just delete it or commented it out.
And then “Add to Cart” button will be back on holidays too for your store.

If you cant do that yourself please send us ftp and wp-admin access at support@byconsole.com we can do that from our side and make it sure for you.