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API URL : https://<shop>.myshopify.com/admin/api/unstable/graphql.json
Same Error i get, but not get any solution still,have you got any solutions? if YES then pls provide me to.Thanks.
I think that you're using the wrong API schema. Cart queries are only available in the Storefront API, and in your example you're asking Admin API for the Cart.
Try removing /admin from your URL request like this
Also check the headers you're sending. The correct name for your request's header should be X-Shopify-Storefront-Access-Token, and of course you should use the Storefront Access Token for those requests as well.