API Error (Client side)

I am trying to use API Action and/or API Data Source components in a project and have hit a bit of a snag. I have added an API Action (and also tried API Data Source) in combination with a Bootstrap table. The table adds ok, I can define the API Schema using static values and it all appears ok (returning the correct data in the response window while defining the schema) until I load the page.

The API starts but then errors, returning a ‘Failed to execute’ message. No data is returned to the the table. I am using parameters stored in Storage Manager instead of the static values and have output them to the page to check that the values have been set correctly.

Please help.