To resolve this issue, disable Storage I/O Control and Distributed Resource Scheduler (DRS).
To disable Storage I/O Control:
- Click Home in the vSphere Client when connected to vCenter Server.
- Click Datastores and Datastore Clusters.
- Click a datastore.
- Click the Configuration tab and click Properties.
- Deselect the Enabled option under Storage I/O Control.
- Click Close.
- Repeat this process for all datastores that are attached to the host.
To disable DRS:
- Click Home in the vSphere Client when connected to the vCenter Server.
- Click Hosts and Clusters.
- Right-click the cluster and click Edit Settings.
- Deselect the Turn On vSphere DRS option.
- Click OK.
The license changes should now succeed and you should see the message:
License downgrade. Some features will become unavailable.
Details... Revert to previous key
Note: This is expected behavior. If you click the Details link, you can see a list of features that will be removed as a result of the license downgrade.