Cannot Create a sales order in Dynamics 365 FO

I am trying to create a sales order in Dynamics 365 but unable to do as the all fields in Order header or Line are grayed out and cannot be edited. Please see below image

I can think of 2 possible reasons, 1. Could be becoz of security and privileges or 2. is there any customization done on sales order form

Reason number 3: Maybe your Sales Order “SO-000025797” status equal “Invoiced”?