Hi, Stina.
Very sad that Bonbon has not shown up yet.
In regards to your question:
I have read about PWPs being used to prevent a villager from moving where not wanted, and to make it more likely if not entirely certain that they would move into the 'plot' the player wants.
I have also read about someone not getting a villager because they tried the above trick but were wrong about having a 'plot' available.
In other words, from what I have read, I believe that it is definitely possible for a villager to not move in if the PWPs, existing villager houses, town hall, etc. all combine to leave no open space, or if the only open 'plot' was not made available on time.
But in this case I believe the villager would also send you a letter saying that there was a change of plans, or something of that sort.
Do you think any of this might be relate-able to your town?