I'm still a newbie but do you feed it and why not place it outside where it can be pollinated by the bees and butterflies. The combination of watering, feeding and sunshine will enhance flowering. My lemon tree didn't bloom/flower until September. Now it is covered with flowers and small fruit. I had it outside until last week due to light frosts. Maybe MeyerMike or someone else can chime in with helpful info.
The usual reason is that the tree isn't getting enough light. The tree can grow and survive in a low light environment but it may not flower. Try whatever you can to get the tree more light without making it a lot hotter. But be aware that the changes you make could cause other problems like more pests or leaf drop.
Where did she say it is not getting a certain amount of light? I am sorry if I missed that. If not, then it will never flower, as everyone says..
Coleen, does your staement mean it has only ever been an indoor plant and that it gets barely any sun?
If it is getting plenty of light and sun, then I would make sure it is not from seed. If so, all the sun and fertilizer in the world will not make it flower for years to come..Sorry..:-(