DIAGNOSIS E01 is Ninja's generic error for a motor overload or overheating. The thermal protection has kicked in because the motor got too hot, usually from extended high-speed blending or a very thick mixture.
FIX Unplug the blender and let it cool down completely—give it at least 30 minutes to an hour. When you restart, change your blending technique. For thick mixtures like nut butters or frozen desserts, use the 'Pulse' function in short bursts rather than a continuous high-speed run. This gives the motor time to manage heat. Also, make sure you're not exceeding the 'Max Fill' line on the jar, especially for heavy tasks.
IF THAT DIDN'T WORK If the error pops up immediately on startup with an empty jar, the thermal sensor or motor itself might be faulty. Try the reset from the previous question (full unplug for 60 seconds). If E01 persists on a cool, empty machine, the base likely needs professional service.
HEADS UP This blender's motor is powerful, but it's not designed for marathon non-stop blending. Think of it like a sprinter, not a distance runner. For multi-minute blends, plan on breaks to let the motor breathe.