FT virtual machines in a cluster that is enabled with vSphere DRS do not function correctly if Enhanced vMotion Compatibility (EVC) is currently disabled.
Because EVC is a prerequisite for using DRS with FT VMs, DRS does not place or evacuate them if EVC has been disabled (even if it is later reenabled).
When EVC is disabled on a DRS cluster, a VM override that disables DRS on an FT VM might be added. Even if EVC is later reenabled, this override is not canceled.
If DRS does not place or evacuate FT VMs in the cluster, check the VMs for a VM override that is disabling DRS. If you find one, remove the override that is disabling DRS.