Diagnosis
You are likely in the high-speed, low-torque gear (setting "2" on the selector). This drill has a 2-speed transmission. Spade bits require high torque.
How to Fix It
Stop. Slide the gear selector next to the trigger all the way forward to setting "1". This is the low-speed, high-torque gear. The drill will have much more mechanical power for boring and driving.
If That Didn't Work
Check the torque adjustment collar behind the chuck. If it's set to a low number or the drill/driver icon, it will clutch out. Turn it to the highest number setting (like 20+) or the drill bit symbol for maximum torque.
Heads Up
This is a 12V compact drill. It is not designed for large diameter hole saws or continuous heavy framing work. Let it cool between demanding tasks.