There are two possible causes of the issue. Either the wrong credentials were used to execute the task or the Acronis Service user "__acro_subst_user__" was not added to the "Replace a process level token" policy during the installation of the agent.
Acronis True Image launches the TimounterMonitor.exe, TrueImageMonitor.exe and schedhlp.exe processes for every user who logs on the machine where the product is installed
This article describes the step-by-step procedure of deployment
Update Acronis Scheduler and recreate the tasks