Windows 8.1 cannot be activated.

My PC has Windows 8.1 Pro installed and is in regular use. When I checked the System section in the Control Panel, I discovered that Windows was not activated. Since I no longer had a record of the product key, I used the Media Creation Tool (MCT) to retrieve the details, which were as follows: Product Name: Windows 8.1 Pro, Product ID: xxxxx-xxxxx-xxxxx-AA989; and Product Key: GxxxD-8xxxH-FxxxX-CxxxD-9D6T9. These MCT results matched the data shown in the System menu (where the Product ID is xxxxx-xxxxx-xxxxx-AA989) and the "Activate Windows" menu (where the current product key ends in ****-9D6T9). However, when I attempted to activate it by entering the product key and using the online activation feature, the process failed, and the notification "Windows can't activate. Try again later" appeared. Repeated attempts to activate it were unsuccessful, and the same notification kept appearing. I would appreciate a solution. Thank you.