sandbox:%20/mnt/data/%20Task_13_Solution.x1sx

I tried to open that path, but there’s no file in sandbox:/mnt/data/ right now (the folder is empty), so I can’t read Task_13_Solution.x1sx.

Please do one of these and I’ll jump in immediately:

1. Upload the spreadsheet file directly in this chat (paperclip / drag-and-drop), or
2. If you meant an existing file already in the sandbox, paste the output of:

bash
ls -lah /mnt/data

Also: your filename ends with .x1sx (with a “1”). If that’s a typo and it’s actually .xlsx, upload the correct file version.