Once the code is inserted and saved, refresh the GSDT to run the test again to ensure that the product schema and aggregateRating is showing up well. There should not be any errors present in the schema In cases where metafield is not present in a Shopify store (syndicated stores) A different set of rich snippet codes needs to be installed, which rely on pulling the review data from widget directly instead of the Shopify metafields:

FireFly 2+ Mouthpiece (2 Pack)

Regular price $15.00
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FireFly 2+ Mouthpiece (2 Pack)

Original FireFly 2 replacement mouthpieces. Each package contains 2 pieces. Micro-particulate screens included. BPA Free.

Compatible with FireFly 2 & FireFly 2+.