The automatic discovery of interfaces would have failed due to the following reasons.
Note: If the problem exists even when the above said conditions are satisfied, go to Settings -> Tools -> MIB Browser -> IF-MIB. Query the device using both device DNS Name and IPAddress and check for the device response. With the necessary logs contact our support team at support@opmanager.com for further assistance.
Related help pages:
How can I discover the interfaces associated with my device?
How do I rediscover the interfaces associated with my device?