On my Jenkins I configured:
Source Code Management
Git repository: https://bitbucket.org/username/project.git
credentials: username/
I second the statements here that say we do not need POLL SCM option with "Build when a change is pushed to BitBucket" but we need to make sure that webhook created in Bit bucket is correct.
Settings I used in BitBucket are: Repository Settings -> Webhooks
1. Title:
2. URL: https://jenkins_server_ip:8443/bitbucket-hook/
3. Status: (Tick) Active
4. SSL / TLS: (Tick) Skip certificate verification (Not ticking this was causing no auto-trigger in my case)
5. Request History: (Untick) Enable request history collection
6. Triggers : (Tick) Repository push
Hope this helps!