Which version of LMS are you talking about?
"no value set" refers to the fact that in DCR the device has no value assigned for the specific item;
where do you have set the ssh credentials? Check the following:
Common Services > Device And Credentials > Device Management
select the device and click "Edit Credentials", check if the Primary Credentials are set (Username and Password);
you can also select a group of devices (like "All Devices") to change the credentials in a bulk.
If you will be set directly into priv 15, no enable password is needed;
if your LMS tasks are working fine (Inventroy Collection, Config Management) "no value set" is just an information that this item was selected for a test, but in the database (DCR) is no value - typical a "Device Credential Verification Job" produces this kind of message.