500 Errors when creating a project

Whilst adding a project in CircleCI to integrate with an internal bitbucket cloud repository, i am able to see the project, however, when I select ‘Start Building’ the UI states, ‘failed’.

In the network output I can see:
https://circleci.com/api/v1.1/project/bitbucket/XXXX/XXXXX/follow 500 (Internal Server Error)

Has anyone encountered this before?

Is there anything in the response body, e.g. an error in JSON?

just

rollbar-4fcef5ccc29985d4878f2e7c5676180b.min.js:2 POST https://circleci.com/api/v1.1/project/bitbucket/XXXX/XXXXX/follow 500 (Internal Server Error)