Uh, ehm, let me just take you aside for a moment here. xD It's your experience, so of course you wouldn't be able to say anything else, but there are a LOT of bi people who are attracted to, well, everyone lol
In general, bi and pan overlap quite a lot when people label themselves. Originally, bi is "attraction to two or more (!) genders", and pan is "attraction regardless of gender". So a gender neutral person can still fall under the umbrella "more genders", basically. So your character can identify as pan or bi and for the robot love, it wouldn't make any difference in my book.
I used to identify as pan, as well, but over time realized that it doesn't quite fit, since I have strong preferences (cis/trans women and genderqueer/nonbinary ppl, to counter the "bi people like boys and girls" argument—I don't dig men... like, at all :D).
These might be things you could look out for, but other than that, I think it's just important to make sure that the humanoid robot really is believable as a person. What makes a person? What makes them, specifically, a person? What qualities does your MC like in them? Etc.
It can be intriguing, so keep working on it, and don't forget to ask for some sensitivity reading afterwards! 

@punkarsenic how dare you beat me to it lol (and @CMYKat, too, WHY ARE YOU FOLKS SO FAST xD)