See if the linkage has popped off, under the scuttle panel, you will see the linkage off if it has, otherwise they will be conencted as they should be to the wiper motor area linkage.
If that is on remove the arm not working and ensure the shaft the wiper goes on is turning back and forth as it should, if it is, it may have stripped the centre of the arm threads, all is not lost however, the spindle will be ok as the armis the softer part so goes first, so put some strands of wire through the hole through which the spindle goes when fitted and force on the spindle, then tighten down as usual with the 10mm nut, this works as it makes a very tight joint.
No doubt caused by the recent snow ice etc, just use the straight edge of the ice scraper to push on the blade along it's length before switching them on will stop it happening again, also useful pressing in the door seal rubber to break ice seal whenthey are jammed shut.
tabetha