Hi Wilfried,
I would check a couple of areas further.
1. The Resource Pool you created in vCenter should have some storage assigned to it like a datastore with enough space for your Clones/Copies.
2. The resource pool also needs to have the LVM_Appliance role permission on it - on vSphere client (browser one), go to Hosts and Clusters and look for the Pool that you want to create your Clones in and select the group that it is in - check the manage/permissions tabs to see lvm-user is there and then the datastore tab to see what datastores are there and if you have enough space - you may have to create one for that group.
3. When you do the clone in LVM it will prompt you at one screen for the Pool that you want to place the system in - you have to select it and then press next screen. In mine I have a Prod and QA pool - it defaults on Prod because that is where you have the prod system deployed but you have to then open the group for QA and select the QA pool as the location for the Clone.
