Do 2 jobs, staple the first at the top left, and one at the bottom left.
It probably will do neither or one won't work. If neither, the cartridge is bad, if only one, the bracket isn't moving it to position.
When I turn on the printer, or press the green energy saver button, the machine begins its initialization procedure and R1 stapler (I assume) staples 25 times, then stops, and the initialization procedure completes. At this point I can use the machine. During the initialization period, the consumables screen shows R1 as "OK," but after the initialization procedure completes R1 is changed to "Error."
I checked the R1 cartridge and it has staples and doesn't appear to be jammed.