NAT type, 2.4 GHz v 5 GHz, and G vs N

To Samuel3201 point and your question about 2.4/5 GHz simultaneous. The xbox 360 will not be connected with 2.4/5 GHz simultaneously. Your router being 2.4/5 GHz simultaneous/dual band just means that it will be able to route traffic on both the 2.4 GHz
and 5 GHz clients at the same time, but not combine them. Think of it as the router having 2 phones and talking to 2 people at the same time as opposed to only have a single phone talking to one person, hanging up and calling another. Also xbox has only released
wireless adapters that are compatible on both 2.4 GHz and 5 GHz using the standards b/g (2.4 GHz) a(5 GHz) on the old wireless adapters and then the new wireless adapters can do those other standards plus n(2.4/5 GHz).

I should mention it only work 2.4 GHz in G......not N

Hi have connected direct to router with Ethernet cable tried 2.4 ghz 5 ghz but nothing have no issues online with ie fortnite nat type open connected to ivp4 and ivp6

If you’re using a wireless network, use a 5 GHz 802.11 AC or N network if possible

Newer wireless technology will give you the best wireless experience when streaming games from your Xbox One console to your Windows 10 PC.

Some wireless routers will broadcast two SSIDs (network names): one as a 5 GHz network and the other as a 2.4 GHz network.

5 GHz networks are less prone to interference from things like cordless telephones and microwaves. Even though 5 GHz signals don’t have the ability to penetrate dense walls like 2.4 GHz signals, it’s always better to try using the 5 GHz band of your network
before using the 2.4 GHz band.

Try restarting your console and see if that sorts it out, if not, please try changing the network frequency on your router settings from 2.4 Ghz to 5 Ghz or 5 Ghz to 2.4 Ghz.