Leds jvc LT32DR530
You do not comment on the type of LEDs, but I think you had already asked, I think you said that each strip has 40 LEDs, if it has 3 cables it means that it brings 2 positives to feed 20 LEDs of the strip with a single common, if the that you are going to bring only 2 cables indicates that all the LEDs are in series, and the voltage that comes out of the source will not be enough to power them, try to upload a photo of the strips with everything and cable .... greetings.
You can make a modification, of course, but the image is important, I don't know why you don't have the option to upload images really is simple, I would like you to comment on the power you have for the LEDs, of the 2 positive ones with respect to earth , this voltage would indicate to us how many leds they are.
with that voltage the dc dc converter for the voltage of the LEDs is not working for you, the 24v must rise to a higher voltage to power the LEDs, maybe your LEDs are good, and your fault is another tell me how you tested the LEDs and If you have a tester for them.
The voltage should appear even for a few seconds even without the LEDs, comment how many LEDs each bar brings, if they are red LEDs with diffuser or thin LEDs and together without diffuser they go either on the top or bottom of the TV, also if the LED voltage comes directly from the source or brings the converter on the screen.
The original brings 40 leds each bar and they are thin rectangular without diffuser. These go on top of the TV. The voltage comes out of an inverter insert separated from the main source plate, from the source a connector goes to the other insert. Too bad I can't upload photos
arm this led tester with disused components if you have 120v in network use the one that brings the filter filter 250 , if you have 220 use the one that brings the 450v filter
Here a tutorial on how to use it you can try a single LED or the complete strip, if you use alligators with a multimeter it will mark the consumption either a single LED or the complete strip in this way you will know how many volts it works.
https://www.youtube.com/watch?v=fBNaDG8Hofw&t=656s