I have 3 "reservations" from servers that needed to be upgraded and I cannot exchange them

A reservation can show 0% utilization after the VM size changes because the reservation no longer matches the resource SKU. In that case, the reservation benefit no longer applies, and the supported fix is to exchange the reservation to match the new resource.

The message "Selected product is not available for purchase." means the target reservation product currently isn’t available for purchase for that subscription or region, or the subscription has a quota restriction.

Recommended checks:

1. In Azure portal go to Reservations and open each reservation.
2. Confirm the old VM SKU no longer matches the upgraded VM SKU. A SKU change is a documented cause of 0% utilization.
3. Try the exchange flow again:
   • Reservations
   • Select the reservations
   • Exchange
   • Review the return quantity
   • Next: Purchase
   • Check whether the replacement VM reservation appears as available
4. If the replacement product shows as unavailable, check these two documented causes:
   • The reservation product is not offered in that region
   • The subscription has insufficient core quota for that VM family/region
5. If quota is the blocker, review the subscription quota for the VM family in that region.

Important exchange rule:

• The new purchase currency amount must be greater than or equal to the amount returned. If the new purchase amount is less than the refund amount, the exchange fails.

If the upgraded VM size is in a different size, series, region, or payment frequency, the new reservation term is reset for the new reservation.

References:

• Self-service exchanges and refunds for Azure Reservations
• Troubleshoot reservation utilization
• Troubleshoot reservation type not available