Can you see any entries in the app-ca.log file(s) around the time you were trying this? Also have a look here:
https://knowledge.broadcom.com/external/article/126420/api-errors-known-causes-for-clarity.html
And follow the links. The one that could assist you is this article:
https://knowledge.broadcom.com/external/article/135699/clarity-api1019-error-when-trying-to-ope.htmlAPI-1019%20Error%20when%20trying%20to%20open%20a%20project%20in%20the%20Modern%20UX
Scroll to the bottom of it and it says:
Tip: The API-1019 error code can also mean you are attempting to use a Studio attribute in the New User Experience that does not have a valid REST API alias name.
- Make sure attribute has a valid API Attribute ID in Classic UX (Administration --> Studio --> Object --> Attributes ) This is the attribute id used in the REST API.
- Set this to make the attribute available via the REST API.
Paul