I identify as bi and I'm open to just boys and girls. I see bisexual as people who are interested in more than just one gender however may not be into everyone or might be into certain genders based on aspects they like about it. While a pansexual person would not even take gender into account.
I feel like with your story, you should focus more on the romance aspect and less on the whole "he likes the computer because he is pan". It reminds me of issues I have with Rick from Rick and Morty being defined as pansexual due to having a relationship once with a genderless/genderfluid being yet not really showing any signs of him being so outside of that one relationship. I dunno if the sexuality of your character really matters with a story about a robot.