I'm just bad with social cues man. No clue why, but I have a hard time reading people unless it's so incredibly obvious that even a blind person could see it. I'm slightly better at it IRL, but fictional characters are tough sometimes.
I'm good at detecting "twist" villains and strange things. Like all of Harry's tells for instance. You go out to eat/hang out with him and suddenly some weird shit happens. Yeah, THAT I can piece together as being strange/suspicious/weird/ a telling sign of something being off. But with more subtle things I just can't read them at all. Sometimes I can notice some body language or the character's smile disappearing when something is said, etc.
But for the most part I just can't really pick out any cues like that. I also seem to struggle with idioms, poetic/philosophical things, as well as hidden meanings behind words. If I think a sentence has a different meaning than what is actually said, I end up rereading it like 20 times until I either give up or am satisfied with whatever explanation I came up with.