The error message 'Unity failed to return license' typically arises due to several potential issues:
Network Connection: The Unity licensing server may not be reachable if there's an issue with your internet connection, or if firewalls or VPNs are interfering with the communication.
License Usage: You may have used up your allotted number of Unity licenses, or your current license could have expired.
Software Bug: Sometimes, it can occur due to a bug in the Unity software. This is particularly common with beta versions or right after major updates.
Local License File Corruption: Occasionally, local files related to Unity license management may become corrupted. This can prevent the application from correctly interacting with the licensing server.
Resolving the 'Unity failed to return license' issue involves troubleshooting based on the possible causes:
Check Internet and Network Settings: Ensure that you have a stable internet connection. If you're using a firewall or VPN, try disabling them temporarily to see if they're causing the connection issue.
Manage Licenses: Visit Unity's license management page to check on the status of your licenses. If your license has expired or if you've used up all your licenses, you'll need to renew or purchase additional ones.
Update Unity Software: If you're using an old version of Unity, or a beta release, try updating to the latest stable release. An update might contain a fix for your issue.
Clear Local License Files: Try manually deleting the local Unity license files and then reactivating Unity.
Remember to backup any important data before deleting these files. After deletion, restart Unity and it should prompt you to activate a new license.