When attempting to select an SSH Key under the DSS option on the Connection tab of a Managed System, they are not showing up in the drop down list.
Log into /paradmin, go to Keys > Managed SSH Keys.
Select the key in question and click the Details tab. Ensure there is a Start and End date configured for the key. If there isn't, either modify the key, or delete it and reimport it with a valid Start and End date.
Failure to configure proper dates will prevent the key from appearing as an option on the Managed System's Connection tab.