Data Not Updated in Google Merchant Center

[Prahlad]

I have run eCommerce projects for my clients.

My issue is I have uploaded product feeds though Content API method and I have resolved errors since last 2 months for missing GTIN number for products but still errors are shown.

So why it's happen and how to fix it?

[RhinoFish]

The GTIN could be wrong, you might be omitting the accompanying Brand Name, or it could be a few dozen other things gone wrong.

Look up any item that says the GTIN is missing, and send us the exact message it is giving you about why the item is still disabled.

If you are very, very certain that you have fixed the GTIN issue, then you can request a review, see step 4 here:
[support.google.com...]

CAUTION = If you just start requesting a bunch of reviews, for things that are not fixed, this plan will backfire badly on you. Be certain you have fixed the issues before you ask for a re-review. Once you ask for a re-review, be patient (being impatient will also backfire on you, they get a LOT of requests, and if you become the person who asks too often, when you actually haven't fixed the issues, well, backfire again, badly).