Verdn locks off impact tiers based on the price of your product. If the product price is above certain thresholds, one or more impact tiers will be unavailable. We set these tiers based on consumer research into how willing people are to pay for sustainable products.
Since we are still gathering data on how to optimise the cut-offs for our tiers, you can currently disable the tier restriction for any product within the Shopify app by clicking the "Unlock all tiers" button: