How can I activate Windows with the following information?

I have the following problem:
I wanted to reset my laptop, but the key is not a normal key:
Product Key Channel: Volume: GVLK

I only received the following information from my predecessor:
His first and last name, his date of birth and a kind of key with 20 characters (or 8 and 12 characters)

How can I activate Windows with this information?
(Unfortunately, contact with the previous owner is no longer possible)

Try the key with 20 characters. Otherwise you have to buy a product key. On lizengo you can get some, for example. Which version of Windows are you using?

Windows 10 pro. But the key has to be there to activate it or not?

That looks like a volume key. Should be difficult as a private individual.

If it is Windows 10, you do not need to enter a key when resetting, this computer has already been activated - i.e. With Windows 7, 8, 8.1 or 10!

With this activation, the hardware ID is entered into a database at Microsoft. If you enter during the setup to reset - or actually reinstall cleanly, that you do not have a serial number, then the computer connects to Microsoft at the end of the setup and retrieves the digitally stored license - and everything is OK.

Have done this a lot lately, always worked.

The key is in there too, but it says, "Windows was activated by your organization's activation service."
I thought that with this key an extra activation would be necessary.

Then that's a volume license. There should also be a repair installation without specifying the product key. The license then remains in the possession of the company.

I now realized that I had to be connected to the company's (predecessor's) network. Since it is not possible, the key is probably no longer usable or?

Then you actually have bad luck and you have to buy a new license.

If the PC is new, then it is sure to be there. But if you bought it from someone, it is often (if available) on the original packaging. Otherwise you have to buy a new one.