Virtual Center Appliance pre check failed Error: Source vCenter Server schema validation found an issue.

from the migration log:

2017-08-18 15:31:41.969Z| migration-assistant-5973321| E: ParsePreUpgradeOutput: Error: Failed to discover a system name that is compatible with both your VMware vCenter Server certificate and your VMware Single Sign-On certificate that can be used to migrate to a VMware vCenter Server Appliance with an embedded Platform Services Controller.

2017-08-18 15:31:41.969Z| migration-assistant-5973321| I: ParsePreUpgradeOutput: Resolution: Regenerate your VMware vCenter Server SSL certificate and your VMware Single Sign-On SSL certificate to have a common system name that can be used to migrate your system to VMware vCenter Server Appliance with Platform Services Controller. DHCP IP Address cannot be used as a system name to migrate to a VMware vCenter Server Appliance.

2017-08-18 15:31:41.969Z| migration-assistant-5973321| I: ParsePreUpgradeOutput: Populated AppNetPnid from PreUpgradeOutput: [].

The thing here, you need to reinstall Virtual Center and Update manager.

Reinstall
Backup SSO
https://kb.vmware.com/selfservice/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=2057353

Stop service in VC
https://kb.vmware.com/selfservice/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=1003895

Uninstall VC
https://kb.vmware.com/selfservice/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=1030559

Reinstall
https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2003493