First, reset default program for Ranger with the latest version mBlock. Please refer to FAQ How to reset default program for Ranger with mBlock 3.4.x.
Secondly, update the Makeblock APP to the latest version on mobile device.
Thirdly, replace brand new batteries or fully charged rechargeable batteries for the starter.
According to our test and research, it is suggested to use rechargeable Li-ion battery or rechargeable nickel-metal hydride, nickel-cadmium which can be bought from amazon or local shop. Or Alkaline battery with good quality like Energizer, DURACELL.
Fourthly: temporarily unplug all the electronic modules from RJ25 Ports on Auriga board and connect the Bluetooth again have a try.
Once still the same issue, please contact tec-support@makeblock.com