A Digital Order ID is a subscription code that is necessary for the connection between Solarfox and SMA or from Solarfox to Fronius.
Per the decision of the PV-System manufacturers, the connection to their API now requires a yearly fee to be paid.
More info can be found here including prices:
https://www.solar-fox.de/files/oneo/documents/misc/EN/EN-price-information-SMA-and-FRONIUS.pdf