OKay......unfortunately I have bad news, that printer is OVER 10 years old.
There are no manuals available online, and there is VERY VERY little info about this printer (in the troubleshooting space) available.
Do you still have the User Manual? If not, and since nothign exists online....It will have to be taken in and serviced....if that is even possible anymore.
As they DO NOT make the parts for it anymore, so any parts will have to be procured as a USED part, or another prinetr of same type that can be scanvenged for parts.
I am sorry, but theres nothign that can be done from my perspective.
The only thing i can suggest, is to REMOVE all paper from the machine, and then REseat the paper back into the printer.
That MAY reset the sensor......but odds are the printer has failed......which is normal for a printer of this age.
Thats the best that can be offered.