It is possible that a power surge damaged the TV. An outage can do severe damage, even with individual surge protectors or a whole house surge protector. Although they help, they don't provide 100 percent protection and new electronics are very sensitive these days to those surge/spikes when the power comes back on.
I would suggest either returning the TV while you are in the return window or contacting Onn customer support directly.
One thing I also recommend is connecting a surge protector that shuts off for a specific period of time (usually 4 minutes) when there is an outage to protect from those spikes that occur when power comes back. I have them on all my sensitive electronics including my fridge and they seem to help.
