For a test, run this in your Scheduler task instead of WinSCP:
Program/script: cmd.exe
Arguments: /c dir c:\toupload\* > c:\users\folder\scripts\dir.log 2>&1
What do you get in dir.log?

See also https://winscp.net/eng/docs/guide_debugging_scheduler#file_access

I do have access to this d:\uploadfolder, because I can mapped it with a different letter drive just fine. Plus, I have admin rights on this.
Even I used the full UNC path, like D:\uploadhere-server\sourcefolder\etc\etc\folder\
It's now saying that the System cannot find the path specified. Which is really weird, because I'm able to see it and map to it on a separate drive (Z: drive).

The local account that runs your Scheduler task does not have permissions to access the c:\toupload folder.
Double check that.

Hi,
I tried this command 'put -latest c:\toupload\* /home/user/' from this page: https://winscp.net/eng/docs/script_upload_most_recent_file. I saved it in ex.txt file. Run this under Task Scheduler as follows: program/script as "C:\Program Files (x86)\WinSCP\WinSCP.exe", add arguments (optional as /log="c:\users\folder\scripts\winscp.log" /ini=nul /script="C:\users\folder\scripts\ex1.txt", start in c:\users\folder\scripts\. The script runs fine, but the log says:
Script: No file matching '*' found. (System Error. Code: 5.
< 2020-02-14 11:42:05.177 Access is denied)
Any help would be appreciated.