GTIN Is available in the product page of shopify but still the google merchant center show GTIN is missing in google merchant center. I have tried many solution from community old post but seems not working. Any updated working solution will be thanksful.
If you have barcodes in Shopify, and you are using the free google shopping app built by Shopify, then yes this is an issue with the app. It has now for 6+ months not worked correctly regarding product identifiers. And I doubt they will fix it.
I recommend instead to use a different app such as: https://apps.shopify.com/multiple-google-shopping-feeds
Which does not have this issue.
Thanks for answer paid app is working fine. Please update me if any free solution is available