Stars on Google Shopping

Two different things put stars next to your products on Google, and IFG Reviews covers both in different ways.

Search results. The product page carries structured data (JSON-LD) with the rating and the reviews, from the Reviews block in your theme. This makes the page eligible for stars in Google Search. Test a page with Google’s Rich Results Test.
Google Shopping. Product ratings on Shopping come from a reviews feed you give to Google Merchant Center. This page is about that feed.

Google decides. Neither route guarantees stars: Google shows them when its own conditions are met, and IFG Reviews cannot make it do so.

What the feed does and does not do

It carries your published product reviews. Pending, hidden, spam and archived reviews are left out, and so are your store reviews.
It is an XML file in Google’s Product Review Feed format (schema 2.4), built from your reviews each time Google fetches it. It carries the reviewer’s display name, the rating, the text and the date, and a verified purchase flag only for reviews backed by a real order. No email addresses.
It does not send store ratings. Google takes those from its own programmes (Google Customer Reviews or an approved review partner), and IFG Reviews is not one.
It is available on every plan.

At least 50 product reviews. Google asks for this before it enables the programme.
A Google Merchant Center account for your store’s domain, signed up to Google’s Product Ratings programme with its interest form. Google reviews the application.
GTIN codes (EAN or UPC) in the Barcode field of your product variants. Google matches reviews to products mainly through GTINs. Codes that are not valid GTINs (wrong length or check digit) are left out instead of being sent wrong, and the check in the app tells you how many of your products have one.
Patience: after the first submission it can take 2 to 4 weeks for reviews to go live.

In the app, open Settings, card Stars on Google Shopping, and press Create the feed link.
In Merchant Center go to Products & store, then Reviews, tab Product reviews, Manage product review sources, Add product reviews.
Choose to add reviews from a file, enter the link as a scheduled fetch and pick how often Google fetches it. Google requires a full fetch at least once a month.
Back in the app, press Check what it contains to see how many reviews and products the feed holds and how many products have a GTIN.

A new status of inactive in Merchant Center right after you add the source is normal.

A review you hide or delete disappears from Google at its next fetch: the feed is always the whole set, and Google removes what a feed leaves out.
The link is a secret. Anyone who has it can read your published reviews. Generate a new link replaces it at once, and the old one stops working, so update Merchant Center. Remove the link stops the feed. Uninstalling the app removes it too.
Reviews are matched to the product page on your own domain. A product that is a draft, archived or not yet synced is left out until it is public.
If your store has more than 50,000 reviews, or a very large catalogue, the feed refuses to generate rather than send a partial file, which would make Google delete the rest. Contact support.