@olivierlambert Sorry, I will tell it clearly next time.

@msupport Thank you for your feedback. I will feedback to Vinchin technical team to optimize our software to provide better service in the future.

Why not use professional virtual machine backup and migration software? That will save a lot of trouble, especially when you need to migrate so many VMs

Ensure that the virtual machine is configured to use UEFI instead of BIOS.

Although I didn't encounter your problem, I followed the steps in an article ( sorry fail to post the link) and successfully migrated the virtual machine from VMware to XCP-ng, which was very convenient.

If direct import isn't possible, you can export the VMs from vCenter as OVF or OVA packages (if supported), which can then be imported into Xen Orchestra.
If you have FC storage already configured and accessible by both your VMware and Xen environments, you can create a VM in XCP-ng/Xen Orchestra without a disk, then attach the existing VM's VMDK files stored on the FC storage directly.

If you haven’t found a suitable backup software, you can try Vinchin Backup & Recovery. It can not only back up XCP-ng, but also back up virtual machines on many other platforms, as well as have powerful migration functions. I know this looks like a sales pitch, but it works really well.

Have you ever consider to use a professional VM backup and migration solution, like Veeam and Vinchin? I heard that they perform quite well when delivering such migration process.

You mentioned that you have configured XO to be on the same subnet as the "default backup/migration" network. Are you sure that the network settings are correctly configured? This includes the subnet mask, gateway, DNS servers, and so on. Also, make sure there are no IP address conflicts.
By the way, a few days ago, I successfully migrated several ESXi VMs to XCP-ng with Vinchin Backup & Recovery. It only took a few seconds to finish migration. Maybe you can have a try.

Maybe you can consider to use third-party tools for cross-platform VM migrations. That will be more convenient and efficient.