Clarify the agreement that existed
Identify the promise, policy, schedule, ownership, or shared understanding that applies before assigning blame. For a message about how to follow up on a design revision, use this factual base: summarize the deliverable, version, requested input, owner, and effect on the schedule.
Resolve the next dependency
State what is complete, what remains disputed, and which action would move the situation forward. Give a small set of options and explain which default plan applies if the real deadline passes. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Document without threatening
Do not bury a scope or price change, threaten the relationship, or pretend silence means approval. Use the contract and documented escalation route for legal, payment, privacy, or security decisions. Keep a factual record and describe only remedies you are entitled and prepared to use.