Code is OK, sorting just needed to use localeCompare since you were working with strings.

function orderedCatalogue(array){
    let catalogue = [];
    for (let i = 0; i < array.length; i++) {
        let elements = array[i].split(' : ');
        let product = {
            name: elements[0],
            price: parseFloat(elements[1])
        };
        catalogue.push(product);
    }
    // catalogue.sort((a,b) => a.name > b.name ? 1 : -1);
    catalogue.sort((a,b) => a.name.localeCompare(b.name));
 
    let currentLetter = '';
    for (const product of catalogue) {
        if (product.name.charAt(0).toUpperCase() === currentLetter){
            console.log(`  ${product.name}: ${product.price}`)
        }else {
            currentLetter = product.name.charAt(0).toUpperCase();
            console.log(currentLetter);
            console.log(`  ${product.name}: ${product.price}`)
 
        }
    }
}