Leaves fall and there is some subsequent regrowth but not full.
Unfortunately, the ash tree (Fraxinus species) has been under duress in Eastern Canada for over 10 years due to the Emerald Ash Borer. The following article is taken from a previous Master Gardener response to a question on the ash tree. It provides good information which may be relevant to your situation.
“Unfortunately, your ash (Fraxinus) has probably succumbed to the emerald ash borer (EAB) rather than having gone dormant. This metallic green wood-boring beetle is about 1 to 1.5 cm long. It attacks all native species of ash trees usually killing them within 2-3 years. In recent years the problem has received plenty of media attention. EAB reached the Toronto area in 2007. This infestation has decimated the numbers of ash trees in Toronto.
Typically the beetle burrows into the bark of the tree leaving d-shaped holes. It lays eggs in May from which the larvae emerge and tunnel beneath the bark and feeding on nutrients within the tree. Eventually this destroys the tree’s entire vascular system and you see signs that the tree is in trouble. Foliage wilts, turns yellow and drops. You can do a Google search : “ash tree with borer damage” for images of the problem. For further help in identifying whether or not your tree is infected the following documents will be extremely useful:
https://www.nrcan.gc.ca/forests/insects-diseases/13395 (Natural Resources Canada)
https://www.yourleaf.org/emerald-ash-borer (Leaf -an organization dedicated to the protection and enhancement of the Urban Forest)
If it is determined that the tree is infected it will need to be removed and for that you will need to hire a tree care professional. Here is a link tohelp you find a certified arborist in your area : https://www.isaontario.com/content/public