Q.My Green Gage Tree Has Never Blossomed. The Tree Is About 6 Years Old. It Has A Full Healthy Foliage Of Green Leaves.
The tree is about 6 years old. Last year I got about 5 plums. That’s it ever, why? It gets a lot of sun, but not the morning sun. It sits next to an apricot tree, which goes very well. Is it suppose to blossom, why doesn’t it fruit?

Certified GKH Gardening Expert
If it is planted next to your Apricot, and it does well, then I could guess that it just isn't quite established enough yet.
This can happen to freshly transplanted trees. Sometimes it can take several years to finally see fruit set.
If your Apricot were having trouble, as well, then I would say something was off in the soil. Since this is not the case, then I'm likely to believe that it will produce more and more during the next few years.
Seeing something, even just a few fruits, is a very good sign. It means that it will finally be ready to fruit in the coming years.
Here is an article that will help you with the care of the tree:
https://www.gardeningknowhow.com/edible/fruits/plum/growing-green-gage-plum-trees.htm