Omeka Collection Viewer - API error?

Hello I am trying to use Omeka Collection Viewer. The instructions say that the API must be on in my Omeka. I have put a check in the box to enable API and saved changes.

I have added http://copolkmuseum.org to the of the OmekaCollectionViewer.cml file.
When I launch the Collection Viewer app I get an error “URL error: The provided endpoint may not support the omeka REST API”.

I tested the viewer using the mall history.org and it works.
I contacted Ideum and they suggested API not turned on and sent me a link to mall museum.org/api which shows their API was on. When I go to copolkmuseum.org/api I get an error that the page isn’t found. I have checked the box and unchecked the box in the API section. Either way the copolkmuseum/api page can’t be found.

How to I correct this error so that I can use the omega Collection Viewer app?

Thank you for your help. We are using Omeka 2.5

I resolved this issue and just wanted to give you how it was resolved in case this happens to someone else.

My issue was the Omeka directory was in a sub-directory on the hosting. I wasn’t aware that the site wasn’t built on Omeka like the examples were.
I was trying to access API at “website.org” but I needed to direct it to “website.org/subdirectory” where Omeka was located.