Why would a HTTP 404 occur?

I have a DNN Platform 09.01.01 website where OpenContent 04.02.00 is installed. When I add OC to a page, it never finishes loading. Instead, there are HTTP 404 errors reported for the API endpoints in the console, see below.

Is this a bug and/or something you've seen before? What is the fix for this?

https://example.com/API/OpenContent/InitAPI/GetTemplateState

https://example.com/API/OpenContent/InitAPI/GetTemplates

Following those two 404 errors, the following error is reported by OC:

"fail is not defined"

Here is the line of code reported for that: https://www.screencast.com/t/cmDiUVhx1