Hey,
You were on the correct track, but I think what happened is that you missed the date with her on Day 4 so you never got the option to commit. Make sure that you visit the cafe, meet Maki and especially read the folded note in the inventory before Day 4 evening, which is when Maki will offer the blind date.
We are aware it's not very intuitive and we're looking into updating this part of the game in the next update to remove the necessity of reading the note in the inventory.