Why this alert/warning is displayed:
A backup was manually canceled by a user. This alert notifies you that the last backup of this machine was not completed and your data was not protected at the expected time.

In recent activities, you can see this warning:

Error code: 70
Module: 309
LineInfo: 0xDB6841B7DE05E0D0
Fields: {"$module":"ms_core_protection_addon_lxa64_15879","$line":"56",
"$file":"d:/134/enterprise/managers/gtob/protection/commands/stop/stop_logic.cpp","$func":"CancelActivities"}
Message: The activity has been canceled by user.

When the alert is deactivated:
This alert is deactivated once this backup is started again.

You can either start the backup manually by clicking Run now or wait until it runs at the next scheduled time.