Error 25 is related to the brake sensors, the function of the brake sensors are to cut all power from the battery as an additional safety feature. The error code will flash when the brake sensors are not correctly aligned and therefore affecting the power flow to the motor.
You should remove the brake sensors, test ride the kit to ensure the rest is installed and running correctly. Then re-install the brake sensors if desired.
Check the 'brake sensors' fitting article for more information about how the brake sensors should be correctly installed.