If the z-index property is not working as expected, there are a few things you can check:

1- Positioning: The z-index property only works on positioned elements (i.e., elements with a 2- 2- position value of absolute, relative, or fixed). If your element is not positioned, the z-index 3- 3- property will have no effect.

4- Stacking context: The z-index property is only applied within the stacking context of an element. If an element's parent or ancestor element creates a new stacking context, the z-index 5- property of the child element will be relative to the other elements within that stacking  context. You can check if an element's parent or ancestor element creates a new stacking context by checking if it has a position value of relative, absolute, or fixed, or if it has a transform, opacity, or filter property.

Overlapping elements: The z-index property only affects elements that overlap with each other. If an element does not overlap with any other element, its z-index property will have no effect.

Numeric value: The z-index property requires a numeric value. If you are using a non-numeric value, the z-index property will not work.

Here's an example of how to use the z-index property correctly: