Adding HA Cluster of two 60F to Fortimanager 7.2.5

At the beginning of this year we bought a Fortimanager licence, I have now set up the Fortimanager using a XenCenter vm image from the download area. Now we want to integrate all of our company's Fortigates into Fortimanager, including two HA clusters. I am currently trying to add the first HA cluster, it also appears in the Device Manager but unfortunately the config status is unknown.
When I try to update the cluster, I get the error message "updnotsupport". The HA Cluster is currently on version 7.2.4.

Are there any solutions to the problem?