At the moment, the situation seems to have normalized so you should now be able to get your cop of GTA V: Premium Edition without much trouble.
Rumor has it that a free copy of The Witcher III: Wild Hunt may be up next in one of the coming weeks. This game is five-years old but still very popular, especially since the release of the Netflix series.
We are currently experiencing high traffic on the Epic Games Store.
— Epic Games Store (@EpicGames) May 14, 2020
We are aware that users may be encountering slow loading times, 500 errors, or launcher crashing at this time and we are actively working to scale. We'll provide an update as soon as we can.