The RCD is a safety device that detects and trips circuits if it detects a small leakage current to earth.
Usually at the far left right or middle of fuse board there is a wee lever type switch which will probably have things like ON OFF written on it and beside it a tiny wee push button that says TEST and 30mA, the lever had probably clicked down to the OFF position, unplug your toaster from the wall, push the wee lever on the RCD in the fuse board back up to ON. That will probably sort if not let us know.
My toaster trips the RCD regular as well when a bit of crust falls of the bread and leans against the toaster element. I just tip it upside down over a bin and give it a wee shake, always sorts it, plug it back in and jobs a good un.
There is probably a wee sticker on your fuse board saying to press the TEST button every 3 months to check operation.
Let us know anyway how you get on.