There are many reasons why your request may not have been selected.
The most likely scenario is simply that your request wasn't one of the very few that were randomly selected.
Typically, artists only use Seated.com when they know there will be more requests for tickets than there are tickets available. This means that in almost every scenario, some true fans get selected while other true fans don't.
Sometimes artists will release more tickets closer to the day of the event. It's best to keep a close eye on their social media feeds to ensure you stay in the loop!