You are in artichoke heaven there. The only thing I can think of is that something has destroyed most of the root system. Maybe a rodent or a boring insect. Try digging a hole a foot deep. Does it have standing water in it? If so, your water table may be too high. But the plants in the background look good, so I don't think you have a high water table. I don't think you should try to move it.

The plant actually looks pretty good in the photo, except that one little choke is hanging down. Maybe something got into the stem.

Once every four days? You're lucky its alive. The wilt in sunlight is telling you something..not enough water!. Sandy soils just make it worse. On regular 2-3 times a week with deep soaking,you will have Artichokes that are productive. If just want one barely alive...then water once every four days!
It looks good for now..so you have time to get it going again before summer.

That beach sand not only does not hold water, it leaches out nitrogen very fast. Besides watering more often I would fertilize regularly with the water. Al