Diagnosis
You've got a complete power failure. The most likely culprit is the unit not being plugged in fully or the outlet itself not working.
How to Fix It
First, check the power cord is firmly plugged into both the back of the oven and the wall outlet. Try a different outlet that you know works, like one you use for a lamp or phone charger. If it powers on at a different outlet, the first outlet's circuit or GFCI might have tripped.
If That Didn't Work
The internal thermal fuse might have blown from an overload. This requires opening the unit. Unplug it, let it cool for an hour, then check the back panel. If you're comfortable, you can remove the screws to see if the small, glass-encased fuse on the main wiring is intact. A blown fuse needs replacement.
Heads Up
Never try to bypass a blown thermal fuse. It's a critical safety device. If you're not confident opening the appliance, contact Cuisinart support. They can often send a replacement fuse or guide you to a service center.