If you have a 'Standard' user access and are trying to update who sold a specific item within an order, and an error message with a small error symbol appears, it’s because the order has already been checked out!
Once an order has been checked out, when you have a 'Standard' user access, no edits can be made and this includes editing the commission on the order. If you want to change the commission with a 'Standard' user access, you MUST do this before the order is checked out!
If an order only consists of a product then the order will automatically be checked out as soon as you take the payment for the order. Therefore, for orders that only consist of products please make sure that you're either logged in to the relevant User account or to update the commission before you take a payment!
If you have a 'Spa Manager' access, you will be able to update the Commission tab even after the order has been checked out.