We recently pushed a brand new community from sandbox to production. The community worked fine in the sandbox, but when trying to test it in production:

• we're able to access the Builder fine
• when trying to access the login page, Workspace, or Administration, we simply get the following error: "Not Found (404)"

There is an existing community in production, but we haven't touched it at all. Salesforce Support claims it's an issue with the custom URL, but as far as we know, we're not using a custom URL. The URLs of the communities are:

• https://[orgname].force.com/applicantportal - this is the new community that is not working
• https://[orgname].force.com - this is the existing community

This is blocking a pending go-live - has anyone faced a similar issue and was able to resolve it?