End-users can view activation error messages on the ‘Activation’ page.
1) Open ‘Settings’ on the device
2) Select Update & Security > Activation
Fig. 1: Highlighted – Error message
Following are some commonly reported activation errors:
- Previous version of Windows 10 was not activated before installing the upgrade.
- Windows 10 Enterprise license lapses and the OS has reverted to Windows 10 Pro.
For activation errors such as the ones listed above the end-user (that has administrative privileges) can use the Troubleshoot 
option to correct these errors.