DrayTek Vigor 3900/2960: Let’s Encrypt ‘Domain Verify Timeout’

If you’re unable to generate a Let’s Encrypt certificate for your DrayTek OS router and the error given is ‘Domain Verify Timeout’, check the following:

Under System Maintenance > Access Control:

• Check Enforce HTTPS Management is Disabled for Internet Access Control
• Check Web Allow is Enabled for Internet Access Control
• Check Web Port is configured to use port 80

Under Firewall > Filter Setup 

• Check your Firewall rules allow port 80 inbound

Reboot the router, refresh the DDNS IP, and try again.