Windows OS lost it's product code/activation status

Ever had the problem where your Windows OS lost it's activation status and product code? Well I have, its happened a few times but were easily fixed by using slmgr and the -ipk switch to reinstall the KMS client key or MAK key... Except this one stubborn server...

One of our servers had lost it's activation status and dropped it's product code. We tried the usual slmgr -ipk to reinstall the product code but that didn't work. Also tried the slmgr -upk, slmgr -cpk, slmgr -ato to no success. There was a slmgr switch that looked very promising, slmgr -rilc which should reinstall all the last known good keys. rebooting the server and trying to activate afterwards still didn't work...

Out of some obscure corner in Google I managed to find something that actually worked.

  DISM /Online /Cleanup-Image /RestoreHealth

This apparently fixed a component store corruption (which probably was something to do with the Software Protection service). I then ran a sfc /scannow for good measure (probably not needed). Bounced the server and all was good.

The product code was showing up and we could then use slmgr /ipk to reinstall the KMS client and get our server activated. Remember to keep your servers happy, when they aren't all sorts of weird stuff goes down!

TLDR; Use 'DISM /Online /Cleanup-Image /RestoreHealth' to fix the component store corruption which broke the activation process.