I may not be able to actually help you with getting FlexiSign to run your cutter however I certainly help with additional information on the cutter which may or may not assist to get it running. I am familiar with the KingCut cutters as we have written drivers for them in our SignBlazer software. Firstly I am not familiar with the a KingCut 900. However the latest version of the KingCut cutter which is 3 foot or 900mm wide is a KingCut A36. This is from the “A” Series. Ok, here is what I do know, there should have been a CD from the manufacturer, without this it will be impossible to run this cutter.
This particular cutter has electronics in it that need to be supported by supplemental software. Instead of electronics a lot of the work normally done by the cutter electronics itself is done by the provided software on your computer. Then this software sends the information to the cutter to make it cut. If you do not have this CD then ask the reseller for one. Some of the earlier models of the KingCut actually had a dongle provided with the cutter. This was to protect the software that is installed from the CD. If you do not have this dongle then the cutter is a boat anchor. Later models (A Series) have the dongle built into the motherboard of the electronics.
After you have installed the software from the CD then go to into the cutter setup of FlexiSign and the rest should be very straight forward. If I can help further then contact me here.