Why doesnt the helium currently in the suns core undergo fusion?

The helium in the Sun's core does not undergo fusion because it primarily consists of helium-4, which is a product of hydrogen fusion. While temperatures and pressures in the core are extremely high, the conditions required for helium fusion—such as even higher temperatures (around 100 million Kelvin) and sufficient density—are not met until much of the hydrogen has been fused into helium. Helium fusion, known as the triple-alpha process, will occur later in the Sun’s life cycle, once it exhausts its hydrogen fuel.