Yeah, confirm your controller is also KT otherwise you could be chasing your tail indefinitely,
KT is short for Ketung iirc, many controllers are silver boxes, but KT controllers also come in a down the tube option or in the battery sled (hailong batteries) types too.. If difficult to unbury test the controller/display combo by setting something ? wheel size? saving shutting down, removing the battery and leaving it unpowered for 30 mins to let everything discharge, befor reconnecting the battery and turning on and confirming the setting you changed has remained changed,,
just because your display and controller share a common power and ground connection does not mean your controller is listening to the commands from the display.
But your pic of a bottom bracket is missing the usual pas sensor and it looks like there is an empty socket there too?? or is that from a sensor hidden from view? perhaps more pics,?