Replaced the cable. Now the screen doesn’t work. What could it be

The cable that comes out of the back of my Apple Thunderbolt Display was fraying. I decided that rather than risk a short at some point, I'd preemptively replace the cable. Upon iFixit teardown photos, I decided to replace the cable that comes out of the back of the screen myself instead of paying nearly $200 to get an Apple Service Provider to do it here in Bangkok. Bought the cable on AliExpress for $12. Replaced it. And … no dice. Screen did not come on.

My setup

[MacBook Air] ---- [Thunderbolt Display] --- [Thunderbolt drive] --- [Cinema Display]

with a USB drive and Ethernet plugged into the back of the Thunderbolt Display

Already tried

• Initial thoughts were that the cable was faulty. But then I noticed
  Ethernet came on, the USB drive was mounted, Thunderbolt drive was
  mounted and after a reboot the Cinema Display also come on.
  Obviously, the cable was working just fine.
• Second thought was that I had neglected to reconnect some cables that connect the LCD panel to the main logic board. I checked. Seemed just fine.
• Third was that
  perhaps the cable serial number was somehow tied to the main logic
  board. So I put the old cable back. Still no screen.
• Tried to
  connect the screen using an external Thunderbolt cable, everything
  worked equally well but still no image on the screen.

• Tried 30+
  seconds and 3+ hours unplugged as a 'reset' of the screen. No change.

• Rebooted my laptop. No change.

• Plugged the Thunderbolt Display into
  the drive and then into the MacBook, so change the sequence of
  devices. No change.
• System Information reports under "Thunderbolt"
  the whole chain of devices, but under "Graphics/Displays" shows only
  the internal screen and Cinema Display.
• Using the newly-purchased
  cable as an external Thunderbolt cable works just fine too.

Question

Does anybody have any suggestions on what to try next?

Does the logic board go into some kind of lockdown mode when replacing the cable?
Are there more than 3 connecting flat cables + ground connection between the panel and the main logic board?
Although there is no reason to assume it has been, how do I test the LCD panel to still function given all these flat cable connectors?

Note: There are no Apple Stores here. Apple Authorised Service providers are no help. They suggested replacing the cable and the panel at a cost that is nearly the same as buying a new screen.