Did you purchase a licence? Was it purchased more than a year ago? Have you installed the licence file? See also https://forum.howtoforge.com/threads/migration-tools-your-license-could-not-be-verified.87262/
The error indicates that your server cannot contact the ISPConfig systems to verify the license key. So this might be a internet connection issue of your server or you blocked port 443 outgoing in a firewall. We can not help you with license issues here in the forum. Please contact the ISPConfig Migration Tool support to get help with such an issue: https://www.ispconfig.org/get-support/?type=migration
Additionally, you can try deleting the program and downloading it again, in case it worked before on the same system but is failing to verify the license now.
