Hi,
What is the model number of the TV?
Is the TV’s red standby power LED on, you didn’t say.
If it is not on then check that there is power available to the TV.
Was there a storm or power outage between the time you turned it off and when you tried to turn it on again?
If there is power available to the TV (different outlets tried etc) then there is a problem with the power supply in the TV. Perhaps a blown fuse or surge suppressor etc. Disconnect the power from the TV and remove the back cover and inspect the power board (where the power cord connects to) for any obvious signs of damage.
If the standby power LED is on, did you try turning it on using the TV controls and not the remote control, you didn’t say?
If it won’t turn on using either option then try a power reset and check if that works OK.
Disconnect the power from the TV and then press and hold the TV Power On button (on the TV, not the remote) for a full 30 seconds and then release it.
Reconnect the power to the TV and try turning it on.