You need a complete circuit to light up that light. If you can actually get to the slide out motor wires, take your jumper cables and wires out there and connect to the battery and motor wires. If the slide out moves with just the negative connected, it's the negative wire that failed (most likely), if it moves with the positive connected, it's the positive. If it doesn't move at all, it's the motor.
Mike
2012 Winnebago Impulse Silver 26QP
2005 16.6 Double Eagle
2018 Jeep Wrangler JK
previously Snowbird Campers,
Triple E Motorhome and Fifth Wheel