After you install Acronis Cyber Backup 12.5 on the machine, certain USB drives/keys are not instantly detected. It takes 2-5 minutes for the drive to acquire a letter and be accessible in Windows Explorer.
If you stop Acronis Managed Machine service, the same USB drives are detected instantly.
Hardware incompatibility: some specific devices incorrectly process standard commands issued by Acronis product components.
Activation makes sure you are using Acronis Cyber Backup in the compliance with Acronis Licensing Policy and Acronis end user license agreement (EULA) [pdf]. In most cases, one purchased Acronis Cyber Backup license key allows protection of one physical machine.