Epic Games store is experiencing an outage after being overwhelmed by a massive surge in traffic from eager gamers looking to snag a free GTA V. Epic Games has since confirmed that the huge amount of traffic the online store is receiving is causing the outages, slow loading times, and crashes in the launcher. For those who are still having problems, do not worry, you still have a week to get the free game. For me, at least, the Epic games client is working fine, and I was able to access the free offer.
Source: https://www.bleepingcomputer.com/news/gaming/free-grand-theft-auto-v-offer-brings-down-epic-games-store/