It no longer works.
'Più' — PYOO. One syllable. The accent is on the 'u'.
Use for electronics, appliances, or any item that has stopped working after purchase. This implies it worked initially, then broke — a clear manufacturing defect claim.
'Funzionare' means to work (for machines, not people). 'Più' in a negative sentence means 'any more' or 'no longer'. 'Non... più' is a fixed negative construction. Do not say 'non funziona più non' — the negation is only 'non' at the start.
Si è rotto dopo due giorni.
It broke after two days.
Specifies when — strengthens your claim.
Ha smesso di funzionare.
It stopped working.
Slightly more formal.
Non si accende.
It doesn't switch on.
Specific to electronics.
Italian consumer law (Codice del Consumo) guarantees a 2-year warranty on all products. The seller (not the manufacturer) is responsible. Always claim through the shop where you bought it.