My grapefruit tree froze during cold weather in South Georgia. The tree was only a few years old. The tree looked dead, and eventually snapped off from it's roots easily at ground level. Some sprouts grew from the roots and the new growth is now about 10 feet high several years after the freeze, but it has not produced any fruit since the freeze. Is it a lost cause for producing fruit?
Your grapefruit tree is probably a graft. Hardy root stock, cultivated upper stock...with the snapping of the main stem or trunk at the ground you now have just the root stock growing.
Yes it will grow fruit but the nitrogen versus P and K has to be lower in percentage to promote fruit. What fertilizer have you used? What mulch? Too much nitrogen will stop reproductive growth. Need enough sunlight and a long enough growing season to get mature fruit. Pollinators. The fruit will be far less quality but the tree will be the hardiest type of grapefruit tree.