I need help

This can happen because of an overvoltage when power comes back. All you can do is unplugging power cable for five minutes, and connecting back sometimes.
If this does not work, then the problem is often the power supply unit. On printers with external power adapter you just replace it.
I think MX700 does not have an external power adapter, therefore you may need to call a technician.
You find the number to get repair service on your owner manual, check also your guaranty terms.