If the power amplifier section overheats or detects an overload condition, it will shut down in order to protect itself and the loudspeaker drive unit(s) to which it is connected.
Once the condition that caused the amplifier to activate its protection has passed, the amplifier will automatically resume normal operation. How long the power amplifier section remains in protection will depend on the cause. If the protection operates for more than a few seconds it could indicate overheating which may take some minutes of cooling to rectify.
A long delay (10 minutes or more) could indicate a persistent overload condition (e.g. one of the components connected to the amplifier is faulty). Try switching the product off at the mains for 30 minutes or so and try again. If it remains nonoperational, consult your retailer who can examine your system and determine the source of the problem.