Short answer: because the analysis of your PCN is not yet done.
Explanation: the state "Action needed" means, that all your PCN's mappings are covered by an analysis and that's why the PCN needs actions. If you cannot create an action workflow, the analysis is still in progress and you have to wait until it is done. This is also indicated in the tooltip:
As soon as at least one analysis task is done, you can create an action.
