The error is related to SSL certification. Please make sure you have correctly configured SSL certifications for the source and target sites.
Here is a thread for how to fix the issue:
stackoverflow.com/questions/21187946/curl-error-60-ssl-certificate-issue-self-signed-certificate-in-certificate-cha
Alternatively, you can use ‘WPvivid Manual Migration’ option to migrate the site:
1. Create a backup for your source site.
2. Upload the backup to /wp-content/wpvividbackups directory of your target site by using Upload feature, FTP client or cPanel file manager.
3. Click on Scan uploaded backups and received backups button to display it in backup list and restore it on your target site.