Okay, Pat. This is a good thing then (the contacts being dirty not you on the computer).
Use an ink eraser and clean off the dirty contacts. Go ahead and do both. Also clean off the contacts on the docking station.
The contacts do not have very much force applied to them when the roomba docks. Even a slight layer of anything on the contacts can keep the unit from charging.
Give it at least 8 hours before you try it or let it operate. That will make sure that it gets a full charge.
After that fire it up and see if it performs as it should.
If it runs out of charge before completing its trip back to the docking station then that means that the battery has lost its ability to hold a complete charge and it will have to be replaced.
Please let me know if you need anything else right now.
If not please select a positive rating at this time. You may ask as many followup questions as you like after rating my service at no additional charge.
!!IMPORTANT!! Before you use the bad or poor rating, ask me why you shouldn't!!