Thanks.. your screenshot tells me exactly what I need to know.
Your setup is pretty well exactly as I would recommend.
To fix the problem I am going to recommend a couple of simple changes. If that is unsuccessful then we will need to do a much more radical rearrangement.
1. Change the current setup of the TC internet tab from DHCP to static. Use all the same identical values it has now.
If the IP is the same as it is now.
Only DNS value might be worth changing if it doesn't use the local Router address as the first DNS .. and you can use 8.8.8.8 as second DNS.. google public DNS are really reliable.
Set link-local only for IPv6 .. Internet Options tab at the bottom of the Internet tab.
Click save then click update.
Bonus score .. if you know your way around the DHCP setup of your main router set a DHCP reservation for the TC. This ensures it always has a known IP in the network from the router configuration.
Or to make it simple you could change the DHCP range from 192.168.0.2-xxx (xxx is maybe 254 biggest number).. to 192.168.0.10-xxx that will ensure the TC is never going to cause issues with duplicate IP..
And if you happen to see a item marked domain or similar.
Change it to local.
Here is mine. Yours will be totally different looking.. But it will normally give you a hostname of the router.. plus a domain.. common one is lan or it can borrow from your ISP domain.
This is all bonus stuff.. we will get to it if we need to later.
2. Change over the cord that connects your TC to your main router.. from WAN on the TC to a LAN port.
We have found the WAN port unreliable in certain setups on the TC.
3. In the local network preferences on your MBP change over to link-local only instead of auto for Configure IPv6.
Tell me how that works out.
