Sorry for thedelay in answering.
The top of the printer is called the ADF (Automatic Document Feeder) and is used for faxing. But can also be used for scanning purposes.
The ADF has a little trigger (toggle switch) that must be depressed before the rollers will activate.
This trigger is used to detect if any paper has been inserted onto the ADF.
That trigger might be stuck, or might be broken. Or you might not e be triggering it fully.
You want the paper to be pushed into the ADF slightly.
That is just ONE possiblity that could be causig this issue.
I suggest you have a look at the trigger, and see if it is still intact, but may be difficult to see.
The other possibilities you would need to take apart the machine.
But you can always get around using the ADF, and just use the scanner glass tray, to do your scanning.
While this is a slower process, when you are scanning multiple pages, it does still work.
Actually the scanner glass will yield a better quality image, as it scans at a higher resolution, than the ADF does.