It comes down to two issues: no army to send and no navy to get it there.
The war of Hannibal and the Barcas against Rome was more or less a personal project by that family, who controlled Spain and its resources and built up their armies there. Hannibal's initial thrust across the Alps and into Italy needed to be done because Rome had complete control of the seas.
Rome sent the forces intended to stop Hannibal in Gaul on to Spain, and raised new forces to fight him in Italy. They faced Hannibal's brother Hasdrubal there for some years.
In Carthage proper, there were essentially no troops at all. There was also not much of a navy, or shipping to carry troops to Italy. So when Hannibal's march ended up in essentially a stalemate, there was no way to get more than a trickle of help through the blockade, although it was a constant concern, especially when King Philip of Macedon allied with Hannibal.
After some years, Hannibal's brother faced a deteriorating situation in Spain himself and marched to join Hannibal, as while he had an army there was no other way to get to Italy. He was caught and his army destroyed by the consuls of the year in North Italy.
When Scipio Africanus invaded Africa some years later, there was still no real army in Africa to face him. Hannibal had to be recalled for the final battle at Zama.