Ok so the problem here is that the URL you’re passing in to get the Sheet Id doesn’t have the “gid” part of the URL in it. If there is no “gid” part, 0 will be returned since that is usually the default sheet ID.
If you could, please try copy-pasting the link again from your sheet, ensuring that “gid” is in the query parameters. I can see in your second screenshot that the “gid” is there in the address bar, so you just gotta make sure it’s in the string variable in unreal as well.
The error occurs because it seems you don’t have any tabs in your sheet with a gid of 0, so the default of 0 won’t work here.