Troubleshooting No Internet Access on new UDM Setup

If a new UniFi Dream Machine is not seeing an internet connection, here a few things that can be tried aside from troubleshooting with the ISP to clear ARP cache or make sure they don't need to allow the device past the walled garden. Both involve connecting to the Dream Machine with SSH using the default credentials (root/ubnt). Identify the IP of the UDM and connect using ssh root@IPAddress. If the device is already adopted and the controller is accessible, the default will have been changed. In the controller go to Settings > System > Advanced and enable debug tools. This will enable you to launch the debug terminal from the device settings. If you want to ssh from macOS or Windows, the credentials can be found under Device Authentication in the Advanced properties.

The UniFi CLI is not documented that well so frequently find myself going to All Unifi SSH Commands that You Want to Know — LazyAdmin for a quick refresher.

1. Validate the date and time.
   1. Type in info and press Enter, NTP should show SYNCHRONIZED.
   2. Enter date and press Enter, the current date and time should be reflected.
      1. If not, manually update the date and time with date -u MMDDHHmmYYYY. Substitute month, day, hour, minute, year for example date -u 0304118482024
2. If updating date and time doesn't correct the issue, try manually updating the firmware. Please note this is an advanced process so should be done once other options have been exhausted. The instructions from the KB are below and vary slightly based on device.
   1. UniFi - Advanced Updating Techniques – Ubiquiti Help Center