No LED backlight on half the strips

I recently got a Samsung UN55KU630DF 55" 4k TV for cheap where the backlight was reportedly out. Thought to myself I wanted to try and repair it.

I took the TV apart down to the backlight LED strips and made an LED tester with three 9volt batteries and two wire leads.

However when I would touch the positive and negative leads on the strips with my tester, I could only get the strips on the left half of the TV to illuminate. On the right half nothing would light up when touching the leads on that side.

Is it possible that all the right half LED backlight strips are bad or could there be a different problem? Where should I start? I'm really new to working on TVs so I appreciate any guidance here.

EDIT: I disconnected the main board and LCD from the power board, effectively so that the power board and the LEDs were the only things hooked up. When I plugged it in I found that the LEDs did light up a little, and some were not lit up at all. Does this mean I just need to replace the LED strips?

Thank you!