My Panasonic TV won't turn on

I got a second-hand TV from a friend. Unfortunately, they can't find the remote control for it, but I've been able to turn it on and off through the side buttons. The other day, I fell asleep with the TV still on and it must have gone into rest mode. Ever since, the power button does nothing but turn on the red light in front of the TV, it doesn't turn the actual screen on anymore.

Things I've tried:

- pressing program buttons to see if one will turn on the screen

- unplugged the sockets from the wall for a few minutes and plugged it back in with the power button off

- turned my PS4 on to see if it would trigger the screen to turn on

- pressed the power button for a few seconds to reset it

I've now bought a universal remote control, but the TV needs to be on for me to be able to program it. Does anyone know what else I can try? Thanks!