Sometimes if there was a paper jam and someone removed it without getting all of the paper, then there could be a small piece of paper still in the way of the sensor. If you have any compressed air it might help to blow it out of the sensor area. I have had issues with that in the past as well, so I opened up the area it said it was jammed - gave it a good going over with the can of compresses air, and it seemed to clear out the jam.
It could be a re-allocation of IP address. The best solution to that is to allocate the printer a specific permanent IP address and but the same setting into the port address for the machine on every PC using it
The printer seems to have both USB and ethernet connections therfore any PC or Mac should be able to connect without any problem. You will need to install the compatible driver for your peeing system. This can be found on the manufacturer website. Hope it helps