It is possible that by accessing your Plesk you encounter the following or similar error:
Error: The license key is incorrect. To use the Panel, please obtain and install a new valid license key.
Your license key has expired. To continue using your Panel, you must purchase a commercial license key that does not expire.
When it reaches the expiration date will be automatically extended. In order for automatic updating to be possible, you must allow >connections to ka.swsoft.com. For more information, please see the following help topic.
Solution
To solve this licensing problem, simply click on the Retrieve Licenses on the warning page. Your server will then contact the Parallels licensing system and update your license key. After clicking the button you may encounter a blank page, just close the Plesk login window and log back into your Plesk address.
If the problem persists, do not hesitate to contact the technical support from your customer area.
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