Are you sure you have your ports forwarded if this is on a different machine, if it's on the same machine make sure you're not using the same base port for both
Check to see if it's generating a new crash dump in your Documents folder with the modified executable. It might be a different issue since a crash window didn't open now.
You'll need to install visual studio and run the editbin program on the halo2.exe file using the command below. (ignoring <> and everything inside of it)
On intel devices you'll need to modify the exe so it's large address aware due to an issue with d3d9on12.
editbin /LARGEADDRESSAWARE...
Add option to manually set splitscreen type in video settings
Fix controller issues when using winlator
Restore rename squad option feature from the Halo 2 Alpha
Add interpolation when spectating vehicles
Add UI debug commands
Add network event functionality (logging)
Allow switching grenades...
We made a change that should've fixed it but it turns out it didn't.
We can't support Windows 7 anymore as code compiled with Visual Studio doesn't work on Windows 7.