Why can't Excel open a file when run from task scheduler?

Create these two folders:

32Bit:

C:\Windows\System32\config\systemprofile\Desktop  

64Bit:

C:\Windows\SysWOW64\config\systemprofile\Desktop

Excel needs these folders if it's not run interactively. Create both folders even if you are on a 64-bit OS.

It's likely a DCOM permissions issue. Automating Excel is sometimes fraught with peril...

The only way I've found around issues such as this is to set Excel to run as a specific user through DCOM permissions.

1. Open Component Services (Start -> Run, type in dcomcnfg)
2. Drill down to Component Services -> Computers -> My Computer and click on DCOM Config
3. Right-click on Microsoft Excel Application and choose Properties
4. In the Identity tab select This User and enter the ID and password of an interactive user account (domain or local) and click Ok

Keeping it as the interactive user or the launching doesn't work with the task scheduler unfortunately, even when setting the task up to run under an account that has admin access to the machine.

When setting DCOM permissions, if Microsoft Excel doesn't appear in dcomcnfg try mmc comexp.msc /32

reference