My patio lights are on a dimmer switch. Recently when I press the switch the lights go on and then switch off immediately and stay off. I can press the switch on and off several times and nothing happens. If I hold the switch down the lights flicker but if I let go they switch off. Please help
Sounds like the switch is bad.
As with anything electronic, sooner or later it fails.
Try replacing it with a standard switch to see if everything works as it should. Then you can select a new dimmer if that is the problem.
If the switch worked correctly in the past and the configuration of the patio lights is still the same as before then there is not much else to blame for this other than a faulty switch. Switches wear out and in the case of dimmer switches can even have some of their internal electronic components burn out. From the symptoms that you describe the first course of action is to have the dimmer replaced.
There is the possibility that some recent change in the configuration of the patio lights may have led to the failure of the dimmer. For example if in the past the lights were all incandescent but were then changed to CFL bulbs or LED bulbs then the dimmer may have not been compatible and thus died an early death.