If you are shipping internationally with Hermes, Shiptheory passes not only the shipment/order value to EVRi but also the unit price of the products being shipped. This is a requirement from EVRi.
EVRi will reject the label request if the total shipment value does not match the combined product values. For example, if your shipment total value has been manually set to £10, but you have two products on the order worth £6 each, totalling £12, EVRi will reject the request on the grounds that the values do not tally.
To prevent such rejections, Shiptheory will determine the total shipment value from the products for international EVRi shipments, rather than the shipment total value.
If you have any questions around this, please reach out to support.