Hi jvilker,
I understand that you installed the printer on your MacBook Air and it was working and now it is not working on the MacBook Air or your Dell. I will try my best to help you resolve this issue.
I suggest that you power cycle your network and if you are still having issues then follow the steps in this document for Printer Does Not Maintain Wireless Connection.
How to power cycle network
Follow these steps to reset your HP printer, your wireless router, and your computer.
1.Press the Power button on the HP printer to turn it off.
2.Disconnect the power cord from the rear of the HP printer.
3.Disconnect the power cord from the wireless router.
4.Turn off the computer.
5.Wait 30 seconds.
6.Reconnect the power cord to the wireless router.
7.Wait 30 seconds, or until the router is fully on and ready.
8.Turn the computer back on.
9.Wait for the computer to reload.
10.Reconnect the power cord to the rear of the HP printer.
11.Turn the printer back on.
I hope this information helps, please let me know.
Thank you,