Dear itsrit2016,
Greetings from team eBay!
We are sorry to know that you are facing issues while listing even after updating the GSTIN & IEC details. Please note that once the details are updated, the customer support team reviews the information and this can take 2-3 working days.
We request you to kindly check for the update from the customer support team in your eBay account under My Messages. Also post this it is important that you account is also verified via Payoneer. Once done you should be able to list successfully on eBay for exports from India. For any other issues related to your account, please do contact our customer support team: https://www.ebay.com/help/home
Regards,
eBay INCBT Team