From the cluster settings, open the hosts tab, select all hosts, and run "Reconfigure for HA" to see whether this helps.
If it doesn't work, please post the error messages related to this task.
thanks for your reply.
reconfigure HA tried (only available with ha enabled), but without success. so i disabled HA again.
end with an "timeout" message in vcenter vsphere-client, same as appears on HA configuration (will be enabled).
additionally appears a "vsphere ha-master-agent not found" message
error fdm[369B940] [Originator@6876 sub=Cluster] [ClusterPersistence::DoFetchDataSync] Open of file /etc/opt/vmware/fdm/kvstore failed: No such file or directory
error fdm[3DA7B70] [Originator@6876 sub=Cluster opID=SWI-3ab50c2a] Dead connection for slave @ host-11734
error fdm[5659B70] [Originator@6876 sub=Cluster opID=SWI-427c3c55] [ClusterManagerImpl::RemovePowerOffFile] Couldn't find datastore /vmfs/volumes/53XXXd8 so file not removed
cause: had some dependencies warnings with some vibs like
.... requires com.vmware.driverAPI-220.127.116.11, but the requirement cannot be satisfied within the ImageProfile.
.... requires vmkapi_2_0_0_0, but the requirement cannot be satisfied within the ImageProfile.
they caused the vmware-fdm not to bee updated by vcenter. they had an old version, which seems to conflict with the newest vcenter.
i manually installed die new vmware-fdm vib from vcenter on all hosts and then i was able to reactivate HA again.
this article helped: https://kb.vmware.com/s/article/2011688
additional i had to add the -f (force) flag on the update command.
scp /etc/vmware-vpx/docRoot/vSphere-HA-depot/vib20/vmware-fdm/VMware_bootbank_vmware-fdm_XXX.vib HOST:/tmp/
esxcli software vib list |grep vmware-fdm
esxcli software vib update -f -v /tmp/VMware_bootbank_vmware-fdm_XXX.vib