Can you give more information? You need to find the source of your problem. Is the issue from your laptop not having internet in the first place? Maybe it's your Xbox's fault? Are you sure all the network settings on your Xbox are set correctly? And finally maybe you could post a screenshot or just explain to us exactly what error you get from your Xbox (if any)?

Strangely, I have this problem too.
What laptop are you using and what OS?

I have a feeling an update a few days ago has screwed with the DHCP and auto ip assigning on the Ethernet on my laptop. Internet sharing doesn't seem to work at all now, when going from Wifi to Ethernet.

I tried to restore my laptop to a month ago, but the restore process just hung. Wtf has this update done?
Also I think my ISP has done an automated software update on my router, which could also be the cause of this.

I've been trying for hours to get this working.
Firstly I have manually re-enabled the DHCP server with my Ethernet, and laptop's internet now works when directly connected to the router by cable, however internet sharing doesn't. I have also disabled ipv6 on the Ethernet, as xbox uses ipv4 but this had no effect. Furthermore I changed settings on ipv4 to assign ip automatically and fetch DNS servers automatically, but still no luck.

I've looked on the xbox and the settings I am getting from the laptop are beyond odd. For the IP address, it isn't even slightly related to the segment of the routers gateway. The subnet mask is ****** up and is missing a .255. Then worst of all the gateway is 0.0.0.0, so the xbox won't even be contacting the router.

I ran a /ipconfig in cmd, whilst wifi was turned off, and found out that the ip, subnet mask and gateway are those of the computer and not the router. This means that internet sharing isn't working at all. I suspect some crap update has messed it up.

I have no idea what to do now, apart from wait till another update which fixes it.