Q.Calamondin tree
I planted a Calamondin seed and now the tree is 6 years old but has never once flowered. The parent flowers and bears fruit twice a year abundantly. Both have the same light, watering schedule, fertilizing and same sized pots. What can I do and why hasn’t it flowered?

Seed-grown calamondins may not grow true to type, or they may produce fruit that is inferior to the parent plant.
Also, seed-grown calamondins take two years to set fruit whereas those grown from cuttings are capable of bearing fruit in their first year.
Has your tree had a dormancy period?
Like most living things, calamondin trees respond to environmental cues to determine the best time for rest and regeneration. The propagation process often disrupts this internal rhythm because it relies on artificially enhanced growing conditions, which may cause the plant to go dormant. Although it may seem counterproductive, one way to break the plant's dormancy and promote fast growth is to induce a state of stress. Withhold all water until the leaves begun to curl up, then water deeply so that the entire root ball is saturated. Water deeply whenever the top 2 inches of soil dry out. Within two months, the tree will produce a flush of leaves and flowers.
https://www.gardeningknowhow.com/edible/fruits/calamondins/growing-calamondin-trees.htm