The major reason that nationalism hindered in 1815-1832 were due to the Austrian dominance and the military power of the Austrian army. In the revolutions of each decade, the Austrian military had crushed and overpowered the rebels. For example, in Naples in 1821, the king of Naples after claiming that he had be forced to agree to grant a new constitution out of fear, went and appealed for Metternich’s aid. Metternich was delighted to interfere to make sure that Austria dominance was still strong and italy weak, so he sent the over powerful Austrian military which defeated the rebellion. Similarly, in the 1830's the Austrian army were sent into Modena, where they used a brutal violence to defeat the rebels. As the Austrian military was so strong it was too tough for any revolution to succeed, leading the country to not be unified in-between 1815-1832. Austria had no ideas for nationalism and would destroy it with an chance.
However, there were many more factors that caused Italian nationalism to fail, including the rebels themselves. As each of the six states that rebelled had all different methods and aims on what they wanted for their state. Each one of the states where unique and did not want to help other states if it did not help them. This happened with Naples and Sicily in 1820. Even though Naples and Sicily both revolting for liberal constitutions, Naples decided that Sicily must remain apart of Naples against their own will. In a same way in the 1830 Parma's revolutionary government refused to send help to Modena to protect them against the Austrian army. Which, the revolutions