How to fix a “mismatched” Craft license
If Craft is giving you an error about your Craft license belonging to a different domain, that means that according to our records, your license is already in use somewhere else.
To change which domain your license can be used on, log into your Craft ID account at id.craftcms.com, and navigate to your Craft license (Licenses → Craft CMS). From there you can see the domain name it’s currently tied to, along with other info about your license:
Click the “Change Domain” button to edit the domain name.
Once you’ve updated it, clear your Craft data caches on the site you wish to start using the license on, and then Craft should start recognizing that the license is being used on the correct domain.
Clear Craft data caches from the Settings page (Craft 2) or Utilities → Clear Caches (Craft 3).