I suspect a bit more detail is perhaps needed here before any suggestions can be made…
- What controller device and App are you using?
- What is the router make/model (which version of WiFi etc?) -
- What error message are you seeing and what is the status LED showing?
- Is DHCP enabled on the router?
- Any MAC filtering, or network-segment isolation in place?
- Is the controller device connected to the main WiFi network and not a guest network, or separate WiFi access point?
- What other Sonos devices do you have?
- At what step during the setup are things failing?
In addition to the above, what device are you trying to bond the Sub to, and is WiFi turned on on that device?