Work through these checks in order.
- Check the key. Copy and paste it again and remove any spaces before or after it.
- Check the domain. Enter the key on the site you intend to use. Staging and local copies count as different domains.
- Check the subscription. The license must belong to an active subscription or be in its grace period.
- Check the domain limit. If the key is already active on another domain, deactivate it there first.
- Check connectivity. Your server must be able to make outgoing HTTPS requests to https://testlinkwebsite.world/plugin-stack. Some hosts block these.
Still stuck? Send us the product name, its version, your domain and the exact message you see.