MacBook Pro 13” shows black screen, works with external monitor

Hi

I’ve recently been using my MacBook connected to my TV via HMDI cable without issues, however the other day after disconnecting I couldn’t get the laptop screen to work normally.

The backlit keyboard works but the flashlight test reveals nothing on screen. I’ve tried the various reset options per internet instructions with no luck. Connecting the laptop to an external monitor still works.

The laptop is already secondhand so I’m not covered by warranty; I’m getting desperate at this point!

Thanks in advance.