Update - I was able to fix it today. There were two fixes that I needed to do.
The actual issue had started a few days back that the trunk lock would open with the key remote button and driver's door switch. It stopped opening with the key inserted into the lock. On the trunk lock mechanism, there are two linkage arms, a short and a long one. I had un-snapped those from the ball joints on both ends, and tightened them by turning the plastic pieces clockwise, thinking that this would shorten the distance that the linkage arms had to pull the latch mechanism when the key is turned to unlock. Well it helped somewhat, but I think it threw off the overall alignment. It may have contributed to the plastic piece breaking off later, as it was intact at that time.
First fix - When inserting the key method had stopped working, I didn't remember that when it's inserted and turned, the actuator actually engages to release the latch if everything's working normally. I watched a youtube video in which it was shown, and then I was able to recall. On the driver's side of the trunk door support, I opened up the infamous wire bunch to inspect. As expected, two wires were broken. I patched those, inserted the key and turned it with minimal force and the actuator engaged! Had I done this in the first place, I think I wouldn't have had to replace the bracket.
Second fix - Thanks to Simon (P2B) for loaning me a spare bracket with the plastic piece intact, I replaced it. Everything's working now.
Car and Owner both getting old
Thanks Everyone.
