Earlier today (around Noon EST), Discord announced the release of API v10. This version will not accept traffic on discordapp.com, and will be the default version starting on April 30. The current default version (v6) will be entirely decommissioned on that day as well.
So right now, the options are change the domain name to discord.com or lock the api version to v9 (although v9 will be marked as deprecated at the same time).