Try these in the stated order:

1. Make sure the toner cartridge is properly seated.

2. If the single sheet slot has a door make sure the door is fully closed. Check for a jam or trash in the single sheet slot.

3. If you have a spray can of air try blowing out the interior of the printer. I wouldn't buy a can for just this as it probably wont help.

4. Unplug the printer. Using a spray can of electronics cleaner clean the rollers. Also spray around all buttons and make sure they are not sticking,

5. If its under warranty have it replaced (no one repairs $100 printers).

6. If it still doesn't work give it a decent burial