Two likely suspects Bob:
1) It is not uncommon for the oil line to come off inside the oil tank. To check this possibility, turn the was on its left side (starter side down) and try the manual oiler. If it oil, the oil line has come off and you will have to remove the oil tank to secure a new one in place.
2) The check valve for in oiler inlet can go bad, there are two types, the older saws had a serviceable disc, same one as used on the 10 Series oilers. These are rarely a problem. The later saws had an integral check valve in the oiler and if they fail, the pump needs to be replaced. You can find new pumps on eBay, Max has them, and I have them available.
If the manual oiler works in all positions but the automatic oiler does not, it is likely the piston for the impulse operated pump is sticking. Sometimes you get lucky and can just run the adjustment screw all the way down and back it out again to free the piston.

More typically you have to remove the pump and free it up. It is possible to remove the 4 screws and take the pump out with the saw fully assembled, just remember to remove the manual oiler rod first...
Mark