https://techcrunch.com/2021/10/04/facebook-messenger-instagram-whatsapp-are-all-down/

Global users are experiencing outages on Facebook, including all social networks the company owns, which include Messenger, Instagram and WhatsApp. When navigating to these websites, a server error will appear — Instagram shows a “5xx server error,” which indicates that this is an issue with Facebook’s servers. Users are also unable to send messages or load new content on the mobile apps for these platforms.

It appears that the outage is caused by a DNS (domain name server) fail — this is the naming structure that forms the web’s infrastructure. So, if you try to navigate to facebook.com right now, the internet won’t know where to find facebook.com.