What does 'Quantities are not managed on a variation level in Etsy.' mean?
This warning means that Syncr couldn't update a stock level of a variation because the stock levels of that product are not managed on a variation level in Etsy
In Etsy, you can set stock levels to a product only, even if the product has many variations. Shopify does not allow this - each variation in Shopify must have a stock level.
For example, if you sell a black t-shirt in 3 sizes, S, M & L. In Etsy, you can assign a stock level of 10 to the product itself. In Shopify, you'll have to set a number for each variation, so S, M & L would have to have a specific stock level.
The issue happens when someone purchases an L T-shirt from the Shopify shop - since the Etsy shop has no stock level set to the L T-Shirt, Syncr has nothing to updated and therefore returns the warning above.
To resolve the issue, its best to set a quantity level per variation, this would result in consistent sync between shops.