Ah, apologies. Didn’t notice you mentioned that on your initial post.
If you’re not sure whether changes in general taking effect or not, you can run with debugger attached (as eblade mentioned) or log some data. Or simply change something obvious and see if it takes effect. If changes do work in general, then it’s specifics of online-subsystem that we are probably not aware of. I don’t have experience working with it, so can’t help much.
Regarding debugger problem you mentioned:
You still can run debugger on your project with an engine you built. There shouldn’t be issues when opening your project solution and running debug mode from there. It has to use your compiled engine to run the project by default.
If there is still a problem though, you can open your Engine’s solution and run it with additional command arguments (Debug → {UE5 solution name} Debug Properties), adding the path to your project’s .uproject file will open that project.
If all fails, logging could be a way to learn what’s going on.
Hope someone with experience in that plugin and networking can chime in and give more specific advise.
Hope this helps 