"Unknown Error" when attempting to delete an old device in Device Manager

My problem:

I'm unable to delete an old device from the the Device Manager section of the Orbi app. Attempting to "Delete This Device" within Device Manager yields the following error:

Error

Unknown Error.

The device in question is not connected to the network, so I can think of no reason I shouldn't be able to remove it from the Devices list.

Background:

• I recently relocated our mesh hardware (1 RBR750 router, 2 RBS750 satellites) to a new home and just finished setting it up. The network appears to be running smoothly. I noticed this problem while reviewing information in the Orbi app after the install.
• I can delete other (unconnected) devices from the Devices list. This problem seems to be specific to a particular previously connected device.
• I have restarted all of the hardware in our network, which has had no impact on the problem.
• I have deleted/reinstalled the Orbi app. This also has had no impact on the problem.
• The description under the device name simply reads "Network". I'm not sure what this indicates? Other devices have a description that usually includes a manufacturer and in some cases a device type (e.g., "Apple * iPad")

Many thanks in advance for any help/insight others can offer!