Hello,
Thank you for your report, this is currently a known issue until Bitbucket is able to provide us an API to create user keys. Here is a workaround in the interim.
From https://circleci.com/bb/<Your-Organization-ID>/<Your-Project-ID>/edit#checkout:
- Open Inspect Element in your browser’s developer tools.
- Click Create User Key
- Find the new public key generated in the Network tab.
- Go to your Bitbucket account and add it manually.
Let us know if this work around solves your problem, and feel free to reach out to support@circleci.com
Best,
@zzak