If you've tried the Basic Network Troubleshooting steps and are still having connection issues, the following are more advanced steps you can try.

Firewall Issues

An important area to check is your Firewall settings, to make sure that Core network traffic isn't being blocked or restricted in any way.  A few steps to review concerning Firewalls are:

Update Firewall

In some cases, there may be an update to your firewall pending that could be preventing Core from connecting properly.  Many players will be using Windows Defender by default - these updates can downloaded and installed by simply updating your Windows.  To check for this, hit the Windows key, type Update, and click "Check for Updates".  Any pending Windows updates will be shown there (if there are any).

If you have a 3rd party firewall installed, it's best to check their website to see if there are any updates available.

Disable Firewalls (temporarily)

If updating doesn't seem to resolve the issue, you can try temporarily disabling your firewall.  Note that this is meant to be done temporarily to determine if the firewall is the issue.  To do so:

1. Hit the Windows Key
2. Type "Control Panel"
3. Click on System and Security
4. Click on Windows Defender Firewall
5. Click on Turn Windows Firewall on or off (on the left-hand side of the screen)
6. Under each Network location, select the Turn off Windows Firewall option

Once this is disabled, test your connection to Core again to see if the firewall was causing the network issue.  In any event, be sure to re-activate the firewall to make sure your PC is safe from network threats again.

Start with a Clean Boot

Sometimes there are some background processes or drivers that may interfere with Core, causing the game to not function properly.  One way we can narrow down if this is the case is to have you try to run a "clean boot" of your system.

To perform a clean boot, please follow this Microsoft guide: https://support.microsoft.com/en-us/topic/how-to-perform-a-clean-boot-in-windows-da2f9573-6eec-00ad-2f8a-a97a1807f3dd

Once that's done, if your issue is resolved at that point, follow the guide towards the bottom to single out what program or driver may be causing the issue.  If you can pinpoint that and disable it on startup, the problem should be resolved for good.

Change to a Public DNS

One troubleshooting step that may work is changing your DNS to a public configuration.  To do this:

1. Hit the Windows Key
2. Type "Control Panel" and click the app that appears
3. Select "Network and Internet"
4. Select "Network and Sharing Center"
5. Select "Change Adapter Settings" on the navigation bar on the left
6. Right click on your network adapter and select "Properties"
7. Select "Internet Protocol Version 4 (TCP/IPv4)" and open "Properties"
8. Go to the bottom of the menu and change "Obtain DNS server address automatically," to "Use the following DNS server addresses:"
9. Put in the following public DNS servers, one in each empty field:
   - 8.8.8.8 (is the primary DNS server for Google DNS)
   - 8.8.4.4 (is the secondary DNS server for Google Public DNS)
10. Save your changes by selecting "Ok"
11. Close all open web browsers and applications
12. Hit the Windows Key
13. Type "Command Prompt"
14. Right click "Command Prompt" and run as administrator
15. Type ipconfig /flushdns and press Enter.
16. Restart your computer

These steps will basically switch the way your internet traffic is routed, which sometimes may perform better by using Google's primary/secondary DNS addresses.  If this step doesn't seem to improve anything, you can revisit step 8 and switch back to "automatic" to revert to default settings.

Release/Renew IP and Flush DNS

Flushing DNS will clear any IP addresses or other DNS records from your cache. This can help resolve security, internet connectivity, and other issues. To release/renew IP and flush DNS:

1. Hit the Windows Key
2. Type cmd
3. Right-click the Command prompt shortcut and select "Run as Administrator" from the drop down menu.
4. Type ipconfig /release in the command prompt and press [Enter], and wait a few seconds
5. Type ipconfig /renew in the command prompt and press [Enter], and wait a few seconds
6. Type ipconfig /flushdns into the command prompt and press [Enter], and wait a few seconds
7. Close the command prompt and attempt to connect to Core again.