Almost always one of the following. Work down the list — they are in order of how often each turns out to be the cause.
1 · Check the licence screen
Go to Scroll Studio → Settings → Licence. If the key is not shown as active, paste it in and click Activate. Buying a licence and activating it are two separate steps, and it is an easy one to miss on a busy day.
2 · The key is in use on another site
A single-site licence is held by one website at a time. If you have used it elsewhere — including a staging or development copy of the same site — click Deactivate there first to free it, then activate here.
3 · A change made in the last day
Licence status is checked periodically rather than on every page load, so a change can take up to a day to be noticed. If you have just renewed or just deactivated elsewhere, give it a little time and check again.
4 · Confirm which edition is installed
The free version has no premium effects to unlock, so a valid key on top of it will not reveal them. Under Plugins, confirm the Pro file is the one that is active — see installing Scroll Studio.
Still locked after all four? Email support@innovatewebdevelopment.com with the address you bought with and the website you are activating on, and we will sort it from our end.