VM VMNAME has conflict mac [00:50:56:xx:xx:xx] with deny list, new mac [00:50:56:yy:yy:yy]
During Cross vCenter vMotion, the virtual machine's MAC address is added to a MAC address "block list" on the source vCenter Server. This ensures that the VM MAC address will not be reallocated to another VM by the source vCenter Server to prevent a potential address conflict in case the VM is migrated back.
When the VM comes back on vCenter outside of a vMotion operation, its MAC address is considered in conflict and changed by vCenter.
To reclaim unused MAC addresses from the deny list, please contact the VMware by Broadcom Technical Support for assistance as described in https://docs.vmware.com/en/VMware-vSphere/8.0/vsphere-vcenter-esxi-management/GUID-165479D3-10CD-4DDB-BBBF-B0607FD2E915.html