I was in the same situation, I had bought Start11 via Ashampoo too. For me, the upgrade was not automatic, I had to check my old license on the Stardock website. You can try here: https://store.stardock.com/myaccount/products . If they recognize your key, you should have an update option. If not, you may have to buy a license again.
Hello,
Sorry to hear you are having issues. But, I am not sure why the update button in Start11 don't work for you. It should, except if there is network down issue.
What it will not do is check for upgrade, for example upgrade from Start11v1 to Start11v2.
Thank you,
Basj,
Stardock Community Assistant.