You can use SpaceObServer in a clustered server environment by installing it on one of the nodes. That means that a node fail over is not handled, but scheduled scans will be started automatically after the node is running again.
You can also install SpaceObServer on each node. If you do so, you have to change the observing server for the scanned roots to each of the nodes, or to none. You can configure the observing server in the edit field "Observing Server" in the "Expert Settings" tab of the "Configure Scans" dialog ("Scan > Configure Scans").
Leave the observing service blank to allow any SpaceObServer service to execute scheduled scans. You can enter multiple servers, separated by semicolon (";"). By default, local drives are stored in the database in their UNC convention (e.g.: "C:\" -> "\\<servername>\C$\"). To ensure that each node is able to scan these drives you have to scan "\\LOCALHOST\C$\" instead.
For each node you install SpaceObServer on you need one licence (See General / Registration).
One reason for this could be that your account does not have access rights to the MS SQL server. Even if this is your administrator account, this does not automatically mean that this account has access rights to the MS SQL server. Another possible reason could be that the MS SQL server was not configured to allow remote access or allow access via Windows authentication. Both can be configured in your SQL Management Studio.