If you are running Windows 10 these steps below will resolve the task scheduler issue.
I use Classic shell in replace of the windows 10 start menu
Go to Start, Programs (All Programs), Utilities
Locate the shortcut to Macrium “Reflect”.
Right click on it and select “Properties”
Locate the “Compatibility”Tab and select it
Click on “Change settings for all users at the bottom”
At the bottom of the “Compatibility for all users” tabCheck “Run this program as an administrator”
Click on Okay
Click on Okay again.
If you receive a security warning accept the change.#Step #2
Configure the task to run "Configure for: Windows 10"
See image below