If your Bitdefender VPN is displaying a "RECONNECTING" notice for the past 24 hours, you can follow these steps to troubleshoot and potentially resolve the issue:

1. Restart Your Computer: A simple restart can help refresh the system and resolve temporary glitches. Close all applications and restart your Windows 10 PC.

2. Check Internet Connection: Ensure that your internet connection is stable and active. Disconnect and reconnect to your network to verify connectivity.

3. Disable and Re-enable VPN Adapter:
- Go to Control Panel > Network and Sharing Center > Change adapter settings.
- Locate the Bitdefender VPN adapter, right-click it, and select Disable.
- After a few moments, right-click it again and select Enable.

4. Change the VPN Server: Sometimes issues stem from a specific server. Open Bitdefender VPN and switch to another server location to see if the connection stabilizes - learn more.

5. Adjust Firewall Settings: If your connection is blocked, it could be due to firewall settings. Ensure that your device's firewall settings are allowing Bitdefender VPN:
- Go to Control Panel > Windows Defender Firewall > Allow an app or feature through Windows Defender Firewall.
- Ensure Bitdefender VPN is checked for both private and public networks.

6. Change DNS Settings: Sometimes DNS settings can affect connectivity. You can try changing your DNS to public servers:
- Go to Control Panel > Network and Sharing Center > Change adapter settings.
- Right-click your internet connection, select Properties, highlight Internet Protocol Version 4 (TCP/IPv4), and click on Properties.
- Select Use the following DNS server addresses and enter 8.8.8.8 and 8.8.4.4 (Google DNS) - learn more.

7. Reinstall Bitdefender VPN: If the problem persists after the above steps, consider uninstalling and then reinstalling the Bitdefender VPN. This can fix issues caused by corrupted files or settings:
- Go to Control Panel > Programs > Programs and Features.
- Find Bitdefender VPN, select it, and click Uninstall. Then download and install the latest version from the official Bitdefender website.

8. Contact Bitdefender Support: If none of the above methods resolve your issue, reaching out to Bitdefender customer support might be necessary. They can provide specific instructions or further assistance.

Following these steps should help rectify the "RECONNECTING" issue with Bitdefender VPN and restore your connection.