If you are experiencing this error, it means that at some point, you added the license key to a Mister Horse account.
When a key is added to the Mister Horse account, the key no longer works. You need to use your Mister Horse account instead.
To use your products with your Mister Horse account, do the following:
1. Login to Animation Composer.
2. Open the "Manage Products" section.
3. Download your products if necessary.
Then the products should work fine.
If you cannot see your products in the Manage Products dialog, please make sure you are using the right Mister Horse account.