I have had my Meyer lemon tree since it was 2 years. I had no problem with it. This winter I had some work done on the door of the porch where the tree is. It was extremely cold outside and snowing (around 10° F). The door was open and cold and snow entered the porch area. After that day all the leaves and flowers withered and dried off. The tree has not a single leaf on it now. Is it dead? Will leaves grow back?
Exposure to freezing temperatures most likely killed your Meyer Lemon tree.
Here is an article about Meyer Lemon tree care.