If you're creating a new playbook, it's possible that the name of the new playbook mirrors an existing one. Per the product release docs back on Jan 11th, 2025 - "Playbook names must now be unique across all SOAR environments, as part of updates to support future features. For customers with existing playbooks in different environments that have the same name, there is no need to manually change names. However, the next time you edit one of these playbooks, you will be asked to change the name before you save."
Hope this helps.
Also, if a particular Action is the problem it should be highlighted in red (e.g. if any inputs are wrong)