Yeah it's pretty crazy. It'll probably be like this again next week when they release their next big free mystery game. Luckily, I was able to find a window when it was working to claim mine, but since I already owned the game, it won't really benefit me much but it's free so why not lol.
You do have an entire week to claim it so no need to worry if you can't get it today due to their current server issues.
RE: GTA V: Premium Edition Is Free This Week On Epic Games Store