Starting from release 1.66, all agent versions older than and including 0.55.3 will be deprecated and will no longer work. Make sure to update your agents.
Nobl9 agent (0.67.2)
Here's what changed in the Nobl9 agent 0.67.2:
ThousandEyes test types: http-server-total-time, dns-server-resolution-time, and dns-dnssec-valid