I can only guess what's going on. Your squash's species is Maxima, which tells me that it will grow adventitious roots along the vine at each leaf node. These are in addition to the main stem's root system. You may have a Squash Vine Borer destroying your main stem while the plant is still able to draw water and nutrients from the roots along the vines. It is not ideal by any means but it may be adequate to survive and produce. My strategy would be to make sure there's water and fertile soil along where the vines are growing. They are easily redirected by hand. And maybe not let very many fruits set. Some folks may have advice about surgical removal of the Squash Vine Borer maggots that *may* be infesting the main stem, but I don't have any experience with that.

thank you for your help i did cut away the dying part and by watering good the rest of the plant seems to be living ok