Google Merchant Product Feed Issue

Job ID: 32280643

Budget: ₹1,500 – ₹12,500 INR

I have Woo commerce based E - Commerce Store

I am using "CTX Feed" Paid Plugin to generate and mange Google merchant product feed

My product Feed is showing 2 error which I am trying to resolve

1. Incorrect value [identifier exists] -"This item has an internationally recognized, unique identifier. Submit a valid GTIN, and either set this value to true or remove this value."
2. Invalid value [gtin] -"Use a globally valid UPC"

Steps Taken --
1. I added "GTIN" filed with every product and passes GTIN value to products for whom I found GTIN.
2. I Added "GTIN Identifier Exist" filed with every product and passes True and False accordingly.

But Still I am getting both error


Looking for freelancer who can help me to resolve both issue and can help me with list of GTIN code as well.