Most modern toasters are controlled electronically, and this (the pcb) is the part most likely to fail.
The symptom is often a toaster where the lever will not stay down. (Make sure the toaster is plugged in first, as the lever will not stay down without current to activate the magnetic latch.)
The other common fault is one or more of the heating elements failing. These can be replaced economically on most makes.
For further help with repairs, try www.howtomendit.com