New growth on the original trunks have paused years ago and some branches die. Some new "trunks" have grown from the base bundle, but even those have paused growth and leaves on some turn brown and die. I thought that it may have needed more frequent and / or more water, so I increased that about 2 years ago, but there was no improvement. I also modestly increased annual fertilizer, but that did not help either. Recently, our landscape maintenance guy thought it may be some kind of "bugs or virus" and said he will find a "chemical" to recommend, which I am not yet sure of want type of product he will recommend. I would appreciate your assistance and would be happy to supply tree samples if requested. Thank you!
Unfortunately, we can't accept samples for evaluation, but your local agricultural extension agency should be able to provide that service. Here's their info:
https://www.gardeningknowhow.com/extension-search?zip=92679&radius=20&extservsearchaction=search&submit=Search
This article should help:
https://www.gardeningknowhow.com/edible/fruits/olive/growing-a-fruitless-olive-tree.htm