The backup of free ESXi server virtual machines is not supported due to licensing restrictions.
BDRSuite does not support the free version of ESXi. BDRSuite utilizes advanced VMware vStorage APIs for Data Protection, and these APIs are a licensed VMware feature. Therefore, backups using these APIs are restricted by VMware. To resolve this issue, upgrade to a paid version of ESX or ESXi to perform VM backups without encountering any issues.