There are a couple possible reasons:
Some days Apple's and Google's push notification services can be really slow. We don't know why this happens and unfortunately, there is little we can do to change thus.
Goal notifications can be slow because we wait until the goal scorer is known. It can sometimes take a few minutes before the goal scorer is identified.
In the most popular matches we send notifications to more than 1 million users. If events that trigger notifications happen at the same time in multiple matches, we have to go through millions of notifications and if you are unlucky, you can be last in the queue. We are sorry about this!
If you have any questions about this you can always contact us.
We are constantly working to improve the speed of our notifications.