The error logs you provided indicate that the Proton VPN client is failing to connect to the selected server (FR#180) due to a split tunneling backend not being found and the VPN server being unreachable. Here’s a structured approach to diagnose and resolve the issue on Debian 13 (standard) accessed via SSH:

1. Verify Proton VPN Backend Installation

The warning Split tunneling backend not found suggests that the required backend for split tunneling (e.g., protonvpn-networkmanager or protonvpn-cli) is missing or misconfigured.

Steps:

• Check if the Proton VPN backend is installed: Run:

  bash

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  dpkg -l | grep protonvpn

  If nothing appears, the backend is not installed.

• Install the Proton VPN backend: If missing, install the official Proton VPN CLI or GUI backend:

  bash

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  sudo apt update
  sudo apt install protonvpn

  If you’re using the GUI version, ensure protonvpn-networkmanager is installed:

  bash

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  sudo apt install protonvpn-networkmanager

• Restart the Proton VPN service:

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  sudo systemctl restart protonvpn

2. Check Network Connectivity

The log VPN server NOT reachable suggests a network issue. Verify if the server (node-fr-22.protonvpn.net or 146.70.194.114) is reachable.

Steps:

• Test connectivity to the VPN server:

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  ping 146.70.194.114

  If the ping fails, the server may be down or blocked.

• Test DNS resolution:

  bash

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  nslookup node-fr-22.protonvpn.net

  If DNS fails, try using a public DNS like Google (8.8.8.8).

• Check if WireGuard ports are open: Proton VPN uses WireGuard (UDP ports: 443, 88, 1224, 51820, 500, 4500). Ensure these ports are not blocked by your firewall or ISP. Test UDP connectivity (requires nmap or nc):

  bash

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  sudo apt install nmap
  nmap -p 51820 -sU 146.70.194.114

  If the port is closed, try another server or protocol (e.g., OpenVPN).

3. Try a Different Server or Protocol

The error suggests the server (FR#180) may be temporarily unavailable. Switch to another server or protocol.

Steps:

• List available servers:
  bash

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  protonvpn list

• Connect to a different server:
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  protonvpn connect --fastest

  or specify a server:
  bash

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  protonvpn connect fr#181

• Switch to OpenVPN (if WireGuard fails):
  bash

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  protonvpn connect --protocol openvpn

4. Check Firewall/ISP Restrictions

If you’re on a restricted network (e.g., corporate, school, or ISP with VPN blocking), try:

• Temporarily disable the firewall:
  bash

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  sudo ufw disable

• Use a different port (e.g., TCP 443):
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  protonvpn connect --protocol openvpn --tcp

5. Debugging Proton VPN

Enable verbose logging to identify the exact issue:

protonvpn connect --debug

Look for errors like:

• Permission denied → Fix with sudo.
• Missing kernel module → Install wireguard or openvpn:
  bash

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  sudo apt install wireguard openvpn

6. Verify System Time and Date

VPN connections are sensitive to incorrect system time. Ensure your Debian system clock is synchronized:

sudo apt install ntp
sudo systemctl restart ntp

7. Reinstall Proton VPN (Last Resort)

If all else fails, reinstall Proton VPN:

sudo apt purge protonvpn*
sudo apt autoremove
sudo apt install protonvpn

Summary of Commands to Try First

# Install backend
sudo apt install protonvpn wireguard openvpn

# Test connectivity
ping 146.70.194.114
nslookup node-fr-22.protonvpn.net

# Connect with debug
protonvpn connect --fastest --debug

# Try OpenVPN
protonvpn connect --protocol openvpn

Next Steps

If the issue persists:

1. Check Proton VPN’s  status page for server outages.
2. Contact Proton VPN support with the debug logs.
3. Try a different VPN protocol (e.g., OpenVPN over TCP).