- Make sure the new OpenJDK16/17 is allowed through the Windows Firewall
- Press the Windows Key and type "firewall."
- Click on "Allow an app through Windows Firewall."
- In the new window, press "O" on your keyboard and look for "OpenJDK Platform Binary."
- If you find it, make sure both the checkbox on the left, as well as both checkboxes on the right, are checked. Then click OK and try Minecraft again.
- If you do not find that entry, click Change Settings, then click Allow another app, Click Browse, then navigate to ↓ and click Open, then Add.
C:\Program Files (x86)\Minecraft\runtime\java-runtime-alpha\windows-x64\java-runtime-alpha\bin\javaw.exe
- Click OK and try Minecraft again.
- Changing DNS settings
In some cases, your ISP's DNS (Domain Name Server) may have incorrect records. In this case, switching to Cloudflare's DNS may solve the problem Instructions on how to proceed here
- Uninstalling/disabling software
Try disabling all Hamachi, Antiviruses, and firewalls (especially third-party firewalls like McAfee)
- Try the following on Windows:
- Press the Windows Key, then type cmd.
- Under 'Command Prompt,' click Run as administrator
- Type the following and press Enter each time.
netsh winsock reset
netsh int ip reset
ipconfig /release
ipconfig /renew
ipconfig /flushdns
- Other connections
Try other connections such as mobile hotspot or VPN, or if you don't have a VPN, use Proton VPN or Warp, which are decent free VPNs.