Your loop code is fine, I’ve tested it using the checkbox field inside a post. What is wrong is your ‘$args’ argument variable.
First off, make sure the post type is correct! Secondly, the meta_key is the FIELD_NAME. make sure that is correct as well, from the looks of it, your second key name was off. Also, value => is wrong as well. don’t use %% unless that’s what the value of your checkbox is. Insert the value of your checkbox.
It would also help if you posted a screenshot of your field group for this particular checkbox field.