My WF did not trigger when a Sales Order is created. Config looks like this: Event Based, Before Record Submit, Set Field Value (Before Record Submit). We have some WFs working on the email preferences, all I want to do is to ensure when a sales order is created the 'To Be Emailed' to be unchecked

Did you check your release status and event definitions? E.g. on create checked? on view or update checked? Appropriate Event types and contexts selected? Set to Released? Is it running on the correct record type and sub-types? Try setting to Execute as Admin (just in case). Enable logging if you need to troubleshoot the specific actions, rather than the actual workflow itself executing.