Male has 23 pairs of chromosomes and female has 23 pair of chromosomes. then why don’t an offspring have 46 pairs of chromosomes which is obtained by the fusion of these two eggs

All cells in a eukaryote are diploid, except for germ cells. Germ cells (gametes) have only half the number of chromosomes as a diploid cell—one of each pair—and are termed haploid (n). In a human egg or sperm, there are 23 chromosomes, one of which is an X or Y. The number of chromosomes is reduced from 46 to 23 during the process of meiosis. Fertilization of the egg by the sperm restores the diploid number of 46 chromosomes.

I should also clarify from your question that fertilization does not result from two ova; rather, it is an ovum and sperm.

The combined mass of both