I guess this is something to do with the Darfon setup, battery/batteryholder.
I have no problems with mine with EP801 and shimanos 630 battery/batteryholder.
Have almost ridden 2000km
Hey the SC-En600 does not have Bluetooth connection.
You have some options to be able to Connect to e tube.
Change display to sc-em800
Change assist switch to sw-en600
Buy sm-pce02 and download e tube project on a Windows computer and do a wired connection
Havent tried that config but i guess it is not. I di think it is the firmwire for the components that is not matching so guess you will need the ep801 as shimano say