Shopify API calls limit
Once your eStore has created 50,000 Product Variants, the limit is set to 1000 variants per 24 hour period. Since this threshold is produced by Shopify, Cart2Cart cannot help that. Don’t worry, API calls limit won’t influence any migration results, apart from the data transfer speed. You can wait till the process ends or contact Shopify Support to explain the reasons and ask them to increase the limits for your store.
Note: This limit doesn’t apply to Shopify Plus shops.