What is a common reason why a team is unable to estimate a story?

 In the context of SAFe, a user story is a short description of a small piece of desired functionality written from the user’s perspective. For a team to estimate a story effectively, it needs to have clear acceptance criteria that define the boundaries and requirements of the story. Acceptance criteria are essential for understanding what is expected to be delivered and for determining the effort required to complete the story. Without acceptance criteria, the team may struggle to understand the full scope of the story, leading to challenges in estimation. This is supported by the information found in the SAFe documentation, which emphasizes the importance of acceptance criteria in defining and understanding user stories within the framework1.