I habe this constant problem with my husband. I know him 6 years already. And I still don’t know when he speaks seriously, ironically, playfully etc. I recall my whole story of learning body language and non verbal cues.
As a kid I didn’t want to look others in the face. It felt too close and highly unpleasant. I can describe it now as being paralysed by electricity. It took me a lot of time to analyse how I felt back then. I was told as around 7-8 year old, that I should look others in the eyes. I started looking in their faces. What I saw there were facial features, nose, lips, form of their eyes (only when they didn’t look back) forehead, chin etc. I started obsessing over their facial features and I wanted to remove their skin and flesh to analyze their skulls and I was highly annoyed by them moving around and moving the muscles of their faces, because I couldn’t peacefully analyze their facial features. Then I also drew many “passport pictures” of imagined friends with their full names and data. 
I was was told to stop staring at others. I was even threatened to be beaten by my peers. Do I stopped looking at them. To the point that I struggled to recognize people at all.
then as a teenager I heard the term “body language” for first time. The teacher told us we perceive only 7% of what she says. The rest is how she says, her tone and body language. I was shocked. I thought, but I’m not even looking at her. I had once a book about body language and facial expressions in my hands. I was scared of the amount of pictures showing how people react in various situations.
i can say I’m learning it in real life situations also maybe from movies. Last time I remember I was confused when 6 years ago my colleague looked at me certain way and I couldn’t understand why he made such big eyes. Only recently my husband made same expression, but from the situation I understood that he was shocked. So this is just an example how I learn it. My excellent memory helps me with that. I often recall like “oh, this person gesticulates like xyz from there or there…”
although I have around 20 years of learning the body language and facial expressions topic, I still struggle to properly understand why people have this or that expression, tone etc, and what it means. These are constant confusions and misunderstandings. I made tests, “read mind in the eyes” where my result was pretty ok, 25/36 correct answers and it took me 22 minutes. I wrote it all down. There were also two shorter tests, where I was supposed to distinguish genuine from a fake smile. And there I failed. In total 14 questions and I gave tight answer to 4. And it also took me long time staring at these faces and trying to figure it out. Even though there were answers with exact description of the genuine smile, I was still confused.
Is there any way to learn it and stop being so confused? My sister laughs that I’m already coming close to 40 and still not understanding sarcasm etc. any coping strategies or advice would be appreciated.
sorry for this long post.