Actually, the license which you will get after purchasing the WP Travel Pro plugin will only work for a single domain. You cannot use the same license key for more than one site.
If you use the same license key in the new site which you have previously used in another site, it will generate issue.
So, if you want to reuse the license in another site you have to send in the license reset request along with the detail in link so that we can reset license for you.
If you have any queries, please submit it to our Contact page.