If you are seeing the "Please update the Access Key of these Enrollments" error message in the Azure Enrollments section, you may be tempted to simply remove the old EA. Deleting the enrollment will also remove the data collected under it so it is recommended to keep the EA configured.
You can uncheck the "Access Key Expired Alerts" box on the enrollment setup page to disable the alerts. Leaving the enrollment and disable the alerts will ensure historical data associated to that enrollment remains in the platform.
If you want, you can then remove the EA once it has been more than 13 months after you changed to the MCA as data older than 13 months is no longer visible within CloudHealth.