A project manager receives an escalation from an external group reporting that an expected deliverable...

When a project manager receives an escalation about a deliverable that was actually provided on time, it indicates a communication issue. The next step should be to revise the communication plan to ensure that all stakeholders are properly informed about project progress and deliverables in the future. This helps to prevent misunderstandings and ensures that everyone has the correct information.

References = CompTIA Project+ Certification Study Guide (PK0-005)