It sounds like the M1 is looking for the network it was originally set up on. You'll need to change the network settings of the Slingbox to connect to your network. What I would do is go to that Network Settings menu you mentioned above, click the "Change Network Settings" button in said menu, and follow the instructions it gives you.
You can find the full process here:
If that doesn't work, you can always give the Slingbox a factory reset and get it set up from scratch. You can find that process below (under "hard reset"):
Hope this helps!