The answer to 'why is my shower won't flush' is that there is likely a clog or blockage in the shower drain. This can be caused by a buildup of hair, soap scum, or other debris that has accumulated over time and is preventing the water from draining properly.
Some common symptoms of a clogged shower drain include slow draining water, standing water in the shower, or a foul odor coming from the drain. To fix this issue, you can try using a plunger or a drain snake to clear the blockage. However, if the clog is severe or difficult to remove, it's best to call a professional plumber who can use specialized tools and techniques to thoroughly clean the drain and restore proper drainage.