Hi! I understand that SHAREit on your Windows 10 machine won't open if your internet is on. That’s quite an unusual situation. To help you better, could you please tell me:

- Are you connected via Wi-Fi or Ethernet (wired connection) when the issue happens?
- What exactly happens when you try to open SHAREit with the internet on—do you see an error message, or does the app just not launch at all?
- Have you noticed if this issue started recently after any updates or changes?

This info will help me guide you through the right troubleshooting steps. Meanwhile, here is what we can try initially:

1. Check Network Conflicts: Sometimes SHAREit prefers a direct Wi-Fi connection without active internet, as its peer-to-peer transfers work best on a local hotspot. Try disabling internet access while keeping the Wi-Fi connection active and see if SHAREit launches.

2. Reset Network Settings: Since Windows Key + I opens Settings, go to Network & Internet > Status > Network reset. This will reinstall your network adapters and reset networking components, which can sometimes fix connectivity conflicts.

3. Run SHAREit as Administrator: Right-click the SHAREit shortcut and choose “Run as administrator.” Sometimes permissions interfere with app launches when the internet is on.

4. Temporarily Disable Firewalls or Antivirus: Your security software might be blocking SHAREit when internet is detected. Temporarily disable Windows Defender Firewall and any antivirus programs you have, then try opening SHAREit.

Please try these and let me know the results or any error messages you receive. I’ll guide you further from there!