When a Trial Key expires (or becomes invalid), it will stop access to the Wikitude SDK in a trial mode.
If you have any Studio Projects, you can continue accessing them in your Studio account. Your Commercial keys, Cloud and Studio API access (should you have them enabled) will not be affected.
In case your Trial Key has expired and you need a new one, we'd be glad to review your request. Find out more on how to extend your trial access here. Please note that, while you have an active SDK subscription, you can renew your Trial access for free.