SDL Automation API, .XLS files not converted for target language

Question

Using the SDL Project Automation API, I am attempting to process some .xls files. 
 When using any other file type, the AutomaticTask, ConvertToTranslatableFormat creates an .sdlxliff file. 
 For .xls file, they are ignored, even though the .sdlproj file contains the filename and lists it as "Translatable". 
 When using the same template and files, within SDL Trados Studio, the files are converted as expected. 
 Are there any known issue with .xls files and the API?

Samuel Baldus · Accepted Answer

OK, so the symptoms were: 
Running a scheduled task, on Windows Server 2012R2, which ran a batch file, that automated the project creation containing .XLS files; the .XLS files were not converted to .SDLXLIFF, but were copied to the target folder. 
The cause was the scheduled task setting "Run whether user is logged on or not" was enabled. 
The solution was to enable the setting "Run only when user is logged on". 
I am not sure why this has an effect, but it clearly does. 
I doubt anyone else has the same issue, but there's the solution.

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SDL Automation API, .XLS files not converted for target language