You may note that Numidia didn't change color in Spring: it kept the "neutral" color, while there was just a small colored square behind your unit. This is to emphasize that you own that unit, but not that province (still). If your unit had not moved, or had moved but another unit of yours had backfilled it, then in Autumn the color would have changed.
Note also that once you own a province it will remain yours even if you don't mantain a unit there, and even if someone else should enter it in Spring and leave it in Autumn.
In short: a province changes owner if and only if a new power occupies it in Autumn.

You only take a supply center if you have a unit stationed in it at the end of fall. To take both Numidia and Phazania on the same turn, you would have to have one unit in each at the end of fall. In other words, passing through a supply center during spring doesn't guarantee that you get it.

Hi,

I am a new player and playing in the The Ancient Mediterranean map as the leader of Carthage.

One of my Army was stationed in Thapsus on the first turn.
Spring : move to Numidia.
Fall : Move to Phazania....

And i discover than Numidia has not taken my color.
Therefore i can only build two armies instead of three putting me behind both military wise and negociation wise.

Could anybody explain to me why things turned out that way ?

Thanks.