Spray some electrical cleaning solvent into the switch, can't hurt.
Then work that toggle repetitively, this may clean it.
They get corroded or just plain dirty and will not pass an electric current
any more, simply working them over and over often will clean them up,
use them or lose them.
If that doesn't work, then open the switch.
On a clean surface with a towel laid out to keep pieces from rolling away, carefully open the back.
Support the switch on its bezel so that the toggles are not what it is laying on.
When the back comes off, the toggles will push through if the switch is not held up.
There are springs in there and contacts. just clean the contacts and reassemble.