After disassembling and reassembling, screen stays blank on power up

I was doing a front frame replacement and followed this iFixit guide. I ordered all the proper tools from iFixit to do this, and taking things apart went pretty smoothly. Currently I'm on Step 14 during reassembly where I just reconnected the battery. Step 13 would come next. I decided to test at this point.

When I power on the device, the screen will get power and "light up" even though it is still black. After ~10 seconds the screen (and I assume the device) will turn off again. Occasionally I will hear this error sound. Sometimes the screen shutdown will happen within 1 second. The system fan does not spin.

Things I have tried:

1. Disconnecting and reconnecting the LCD ribbon cable in Step 24-25.

1. NOTE: During first reassembly the cable would insert slightly uneven with the right side further in than the left. I made 2-3 attempts to evenly apply pressure to the "tabs" on either side of the cable with a spudger and opening tool to push the left side in enough to match the right. I was not very successful and the left tab ended up folding down and under the ribbon cable. During troubleshooting this also occurred, but I believe I got the cable seated more firmly in the ZIF connecter.

1. Reconnecting the microSD card reader from Step 10 in case it needed to be attached.
2. Disconnected and reconnected the "Headphone Jack and Game Card Reader" board in Steps 18-23
3. Connected L and R joycons. On boot, button presses would cause appropriate sounds to play from speakers.
4. Held Power for 20-60 seconds to attempt reset, then booted the Switch again.
5. Charged the Switch for 45-60 minutes and attempted boot again. During charge, no battery indicator popped up in the corner of the screen as usual.

None of these fixes caused any change.

My best guess is that everything is connected, but no data is making it to the LCD screen.

Is this fixable? What else can I do to diagnose the issue?

EDIT: I normally play in handheld mode and forgot about the dock. I put the Switch in the dock in its current config, and the console booted and seemed to work normally! It probably is the LCD screen then. How can I diagnose the issue to see if it's a loose connection or if the cable is dead and I need a new one?