## TL;DR
Azure only allows exchanges on reservations in an eligible state, and a reservation already applied to a scope (or past its exchange window) is refused. Check the exchange eligibility, unapply or change the scope if the rules allow, and otherwise use cancel-and-rebuy within the allowed limits.

## Use this when
- The reservation exchange blade errors or greys out.
- You bought the wrong size or region and want to swap.
- The reservation shows as applied to a subscription or resource group.

## Not for this skill when
- A new reservation purchase fails on capacity. That is a capacity problem.
- You want a refund outside the exchange rules. That is a cancellation question.

## Steps
1. Open the reservation and check its exchange eligibility status in the portal. Verify: you see the specific reason it is ineligible.
2. If the blocker is the applied scope, check whether the scope can be changed to shared or another subscription first. Verify: the scope change succeeds.
3. Retry the exchange after the scope change. Verify: the exchange flow proceeds.
4. If exchange stays ineligible (term limits, prior exchanges used up), use cancellation within the allowed window and buy the correct reservation. Verify: the cancellation completes and the new purchase is active.
5. Confirm the new reservation is actually applying to usage in the billing data. Verify: discounted line items appear.

### Prior-exchange variant
Each reservation has a limited number of lifetime exchanges. Verify: the exchange count has not been exhausted before assuming a bug.

Compatibility: Azure Reservations, all eligible services.

## Why it happens
Exchanges are a constrained operation: Azure limits which reservations can be exchanged, how often, and in what state, to prevent reservation churning. An applied scope is one of the states the rules exclude.

## Edge cases / pitfalls
- Exchange limits are lifetime per reservation, not per year. Count them before planning a swap chain.
- Cancelled reservations refund only within the policy window and may carry fees.
- The replacement reservation must be of equal or greater value in most exchange rules.
- Scope changes themselves can take time to reflect in eligibility checks. Wait and retry.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_ee60VGo8SQluUxpWFvbFWw