When a virtual machine is removed from the inventory in the vSphere Client and then re-registered, any previously configured scheduled tasks are lost.
vSphere 8.0, vSphere 7.0
Removing a virtual machine from the inventory deletes any configured scheduled tasks. This is the expected behavior.
After re-registering the virtual machine in the inventory, please configure the scheduled tasks again.
Japanese KB: インベントリ再登録後の仮想マシンでスケジュール設定タスクが消失する