If Online Activation fails, this could be because:
If either of the above is true, Unity will not be able to contact the license server and the Editor will automatically attempt to perform a manual activation.
Follow the steps here to manually activate Unity on your machine:
(Please note that you need to have access to a machine with Internet access as part of this process, but this does not have to be the machine on which you are trying to activate Unity.)
Open Unity. If Unity cannot contact the license server, you will be presented with the following window.
Click the Manual Activation button.
Click the Save License Request button to save the License Request file.
Save the license request file by selecting the Save License Request button. Save the file in a directory of your choice. (Make sure you remember where you save the file. In this example, the license file is being saved in the Documents folder).
Once you press the Save button, the file is saved and you should see the following notification at the top of the window.
The license request file you just created is tied to the machine you generated it on. This license file will not work on any other machine. The license file will stop recognising a machine that has been reformatted or has had hardware changes.
The next steps require Internet access. If your machine does not have Internet access, you can activate your license on a machine that does have access by copying the file to the other machine, activating the license using the following steps, and then copying the file back to your machine to use Unity.
In this example, we are licensing a Plus or Pro version of Unity.
Note: In this window the serial number has been hidden. Click the Next button.
This will open up your directories within your hard drive.
Note: Some browsers may append “.xml” to the license file name. If this is the case, you will need to delete this extension before attempting to load the license file.
If you have already activated Unity and, for example, need to update your license, see the Managing your Unity license page.
For any further assistance, please contact support@unity3d.com.