Запятой после headers {...} не хватает
$.ajax('https://opskins.com/ajax/browse_scroll.php?page=1&appId=730&contextId=2', {
headers: {
"Host": "opskins.com",
"Connection": "keep-alive",
"Accept": "*/*",
"X-Requested-With": "XMLHttpRequest",
"X-OP-UserID": "28044339",
"X-CSRF": "2ADuEWQS6oFljN3veQFbe47lBBYvaI62X",
"User-Agent": "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.84 Safari/537.36",
"Referer": "https://opskins.com/?loc=shop_browse",
"Accept-Encoding": "gzip, deflate, br",
"Accept-Language": "ru-RU,ru;q=0.9,en-US;q=0.8,en;q=0.7",
"Cookie": "blabla=bloblo; blablabl2=bloblo4; aaa=bbb"
}, // ВОТ ОНА ОШИБКА (НУЖНА ЗАПЯТАЯ)
crossDomain: true,
success: function (body) {
console.log(body);
},
error: function (error) {
console.log(error);
}
});