I grew an apple tree from seed starting in 2015. I planted it in 2016. It is now over 6 feet tall and looks very healthy. I have pruned it every year but again this year there is no blossom. Can you please advise me what to do. Thanks.

It takes between 7-10 years before they produce fruit. Also, it won't bear the same fruit as what you removed the seed from, they don't come true to that fruit. It may be good or it may not. Seedling apple trees are genetically different and usually inferior to the parent tree and that's why most trees are grafted.
Long time to wait to see if it is worth growing IMHO.

Thanks Sue