Sago 'Palm' (Cycas revoluta) is a plant that can often display confusing or idiosyncratic symptoms.
I have experienced Cycas losing nearly all their leaves before shortly putting on either a new flush of leaves or a reproductive cone. I have also had Cycas skip their annual flush of leaves for several years before somehoe deciding that it was time to grow some more. Cycas have been known to survive several years without leaves before producing new foliage, though this is not ideal from a horticultural perspective.
Inspect the plant for any visible pests. if none are found, consider the plant's cultural care.
Cycas revoluta can grow well in full sun to bright shade. It needs regular water and good drainage. It often benefits from the addition of fertilizer, as it can be prone to nutrient deficiencies. Do what you can to give the plant this level of care. You may consider lifting up the plant and improving the growing bed by mounding and amending the soil. Be patient. It may take longer for Cycas to respond to treatment than other plants.