Receiving Code Error 1000

When attempting to test an API connection for a collection integrating with Backendless, I’m receiving the following error:

An error occurred when calling Get All

Request failed with status code 404
“code”: 1000,
“message”: “Entity with ID register not found”,
“errorData”: {}

I confirm the Application ID and REST API key are correct from Backendless

Any guidance would be appreciated.