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pptpd.service often shows as inactive due to configuration errors in /etc/pptpd.conf or /etc/ppp/pptpd-options, firewall restrictions blocking TCP port 1723, or the service failing to start due to missing kernel modules like nf_conntrack_pptp. It may also fail if the IP address range for clients is misconfigured. 

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Common Reasons for Inactive pptpd.service:

Firewall Issues: The required TCP port 1723 is closed, or GRE protocol (port 47) is not allowed through the firewall/router, which is necessary for PPTP connections, as described in VIPRE Success Center's guide.Configuration Errors: Incorrect localip or remoteip ranges set in /etc/pptpd.conf, or improper options in /etc/ppp/pptpd-options.Service Startup Failure: pptpd may not be able to create its PID file properly, causing the system to think it's not running, as shown in Ask Ubuntu's thread and Unix & Linux Stack Exchange's post.Missing Kernel Modules: The required PPP compression or filtering modules (like ppp_generic or nf_conntrack_pptp) are not loaded.Service Stopped/Dead: The service might have crashed or was never enabled to start on boot. 

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Troubleshooting Steps:

Check Status: Run
systemctl status pptpd
to see error messages. Verify Ports: Ensure port 1723 is open and GRE protocol is permitted in iptables or ufw. Check Logs: Use
journalctl -u pptpd
or check /var/log/syslog for detailed errors.Restart Service: Try running systemctl restart pptpd and check the status again.Check Configuration: Review /etc/pptpd.conf to ensure proper IP address configuration for clients