Story

Quick Story here, Installed a copy of Server 2019. System is completely offline, how to activate it?

I found a couple guides to help along the way, and even a nice thread post.

Issue

Main thing I found was a command to get your started:

slui 4

To my dismay I was greeted with a greeting, much like the thread poster:

"Can't activate Windows by phone."

If you keep reading there are other potential reasons for activation to fail, but that usually happens afterwards with a dedicated error code. E.G Attempting to activate a evail edition, or using a MAK key instead of a retail one, or using the wrong key with the wrong edition (Standard vs Datacenter).

In the first example it makes sense, as well as the last one. In my case I was using the proper image downloaded from VLSC with the key from the same web portal, So I knew I was good on the first and second examples. The middle example of requiring the use of a retail key didn’t seem right, as I would assume any version would suffice. *NOTE* At this point I was merely assuming, as I couldn’t fully verify my key as I wasn’t utilizing a VMAT server. Again this is an offline activation.

Solution

Now for my realization, I had made yet another assumption, and that was I’d assume slui 4 would provide a pop-up that would allow you to enter your product key before starting, and the error message doesn’t exactly convey that with an incorrect error message of: “Can’t activate Windows by phone.”

When in reality it should have simply stated “Please set a product key first”.

as it turns out you have to use: Windows Software Licensing Management Tool and can be accesses via elevated command line using slmgr.vbs.

Yes that’s right a Visual Basic script. ;P.

C:\Windows\System32> slmgr.vbs /ipk <Key>

/dli (This will show basic license and activation information.)
/dlv (This will show detailed license and activation information.)
/xpr (This will show the current expiration date of the license installed which is most useful when using a KMS key with a local KMS activation server on the network.)
/upk (Be careful with this one as it will uninstall your current license key.)
/cpky (Also be careful with this one as this removes license key information from the registry.)
/ipk *****-*****-*****-*****-***** (This will change your license key to the one entered. If there was no key entered previously this command will also attempt to activate the license based on the license key type.)
/ato (This will force an online activation immediately. This could be useful if you have already entered the new key but was not online with either the KMS server for the network or unable to reach Microsoft’s activation servers.)

After doing this, then running slui 4 again, I was prompted with a screen asking me to select my Region. I then proceeded to use a Phone to call the toll free number provided and follow the IVR prompts to get a confirmation ID.

After entering the confirmation ID, I successfully activated Windows Offline. I did note one thing, that I told the IVR I did not have a smartphone so I did not get the web link as mentioned by others in the comment area. You can save this link and use it to do offline activations without calling in to the phone number from another machine that is online. If I manage to get this link I will share it as the commenters in that other post did not do the same.

Hope this helps someone.