Hi heart,
I would suggest speaking to HP.
I had an envy with the same issue. I racked my brains to try to figure it out only thing that worked for me is to replace it as it was faulty.
My new envy works fine but I'm sure the support guys will assist with basic and advanced printer configurations and troubleshooting that may fix most of the issues.
Other possibilities is that your modem doesn't support being made into a LAN gateway that will let you access other devices on the network.
This can be solved by checking if you see other devices being part of your network eg computers and maybe trying to access them via your network or home group.
If you can then go back to 1st point.
However , I would trying your luck with HP support and see how you go.
Best of luck,
Wayne