Likely causes of this are:

• Incorrect interface selected for monitoring.

  Action: Refer to how Highlight discovers ADSL bandwidth and select an alternative interface or select a physical interface

• (Draytek) Operating system needs an upgrade.
  Pre-2015 firmware does not supply a downstream DSL speed, and Highlight will only respond to bandwidth autodiscovery if both upstream and downstream speeds are available.

  Action: Update the firmware to a more recent version