If you delete a product or variant in Shopify that customers are still subscribed to, it will cause the error saying: Variant removed from Shopify. This could also happen if you change your variant options. Existing customers that point to the old variant_id will not be able to have orders generated, and we don't prep the future orders either since it needs the variant_id for things like shipping rates, SKU, and more.
Simply click this link to view the list of all the variants that are currently missing in the Broken Active section.
Review each product title / variant title combination on this tab to identify which variant or product titles you may have changed in Shopify.
Click fix next to each product title/ variant title combination.
On the next page after clicking fix, identify the replacement product title and then variant title from the drop down lists (or type in name to search and find).
When you find the approriate product title / variant title combination, click Fix Variant to replace the broken variant and automatically retry the charges for all affected customers.