Do you get any logs?
Did you try to follow debugging instructions?
https://winscp.net/eng/docs/guide_debugging_scheduler

Hi All,

is it possible, that scheduled task (Windows 10) is not working on FTP port?
On the server (not my server) there is no SSH/FTPS available.

My scheduled task is working when i run manually. I've read WinSCP-Faq-Scheduler, but not found solution for this.

I've tried:
- run with C:\Program Files (x86)\WinSCP\WinSCP.exe
- run with portable winscp (c:\temp, full right)
- run scheduled task with highest privileges
- run from mentoined folders (c:\program files... c:\temp)
- run with argument (/script="C:\temp\sync_local_to_FTP.txt" /log=C:\temp\log.txt)

Thanks for your every help or idea.