My Etsy variations have no SKU but my Shopify’s do
This is a common issue - since Etsy allows tracking stock on a parent product level and Shopify does not, you might have products in Etsy with multiple variations that share a single SKU and single stock level.
The same product in Shopify will have a unique SKU and stock level for each variation.
Syncr cannot reliably track products in such state. The reason is, if a variation’s stock level is updated in Shopify, Syncr will not be able to find the variation in Etsy and update it accordingly, since the variation’s SKU in Shopify will not exist in Etsy.
To solve this issue, the best way would be to add SKUs and Stock to the product in Etsy. Once the SKUs are added, Syncr will pick up the changes and update its records to ensure that syncing is possible.