I can't tell. Is there any chance this tree is on its own root. If it has never flowered or fruited is it even a lemon tree. If you purchased the tree yourself and know it is grafted my guess it is to far gone to work with. It appears the fruiting trunk has died.

Wow! That IS a complicated trunk! It looks like it's died back to an area about 12 inches from the ground on multiple occasions. It's difficult at this point to tell what was a graft line, if there ever was one, and what is regrowth after a die back. Are you in a zone where you go down in the low 20s for multiple nights in a row? If the tree is non-grafted, it just may not be old enough to fruit, i.e., it may be getting re-set each time it dies back.

Thank you both for your replies and apology for my belated response. At this stage, I am not experienced enough to tell where the grafting line is so I have removed the 2 thin shoots and left the V-shaped trunks and will fertilize well to see how this will change in the next few years. Yes it might not produce at all but the bush is nice looking enough and the leaves still smell of citrus so I am happy to keep it growing.