Why do I get an error '404 Invalid URL' when I try to call any of my function endpoints?

You will encounter this error if you enabled the API Gateway component for your project and did not create any APIs for your function endpoints. After you enable the API Gateway, the URLs of your functions and web client will become inaccessible until you create APIs for them. You must therefore immediately create APIs for your functions and client, or disable the API Gateway from the Catalyst console and then access the application URL to resolve the issue.