Seems everything is working fine now.
If you're wondering what the issue was, Centra seems to send requests with an empty User Agent if you don't set one and I recently modified my firewall to block empty User Agents due to some attacks.
Once that issue was resolved, another issue appeared, specifically involving permission checking. The API checks if the guild has enabled the public feature in Fire with the "$public" command or has the DISCOVERABLE feature but this seemed to be failing. Switching from bigints to strings seems to have resolved it though.