Why do all the host attributes values display "-" after I upgrade my scavenge-ready host to 5.1?

This issue may occur when upgrading a 4.1 cluster to version 5.1 and is caused by activating your cluster when the status of some 4.1 scavenge-ready hosts are "Closed". To resolve this issue, restart EGO on these hosts and when their statuses are "OK", run the activation console to activate them.