The answer to 'leak repair won't flush' is that a leak in the plumbing system can often prevent the toilet from flushing properly. This is because the leak is causing water to continuously drain from the tank, making it impossible to build up enough water pressure to flush the toilet effectively.
Some common causes of this issue include a faulty flush valve, a cracked toilet tank, or a problem with the fill valve. In some cases, the leak may be coming from another part of the plumbing system, such as a leaky pipe or a problem with the wax seal under the toilet. To fix the issue, you'll need to identify and repair the source of the leak.