You could try to promote it in relevant communities. For instance, on forums or social media groups dedicated to robots, science - fiction, or fan fiction in general.
Well, it's a rather rude statement. 'Stfu' is a vulgar abbreviation for'shut the f*** up'. It basically means that the person doesn't want to hear about someone's robot fanfiction, thinking it's uninteresting or not worthy of attention.
Perhaps the story doesn't stand out enough. Fan fiction is a crowded space, so it has to have something unique. It could be the characters aren't developed well, or the plot is too predictable.
Maybe they're just in a bad mood and don't want to hear about anything, especially something as niche as robot fanfiction. People can be grumpy and lash out like that.
Revise and improve your writing. Maybe the story needs some more twists and turns, or the characters need to be more relatable. You can also ask for feedback from a few friends who are into the same fandom. This can give you some ideas on how to make it better.
Perhaps the writing style or the story concept of the fan fiction doesn't appeal to a wider range of people. It might be too specific to a certain sub - group within the fandom. Another reason could be that there is not enough interaction or community building around it.
First, improve your writing skills. Use vivid language to describe the robots and their world. For instance, instead of just saying 'the robot moved', you could say 'the sleek, silver - hued robot glided across the room with a grace that defied its mechanical nature'.