Unable to get Values from another List

Good Morning Plumsail-Team

I may have run into a small Problem when using the DataTable Control in the Forms.
So the requirement i have for this task is to create a list, in which different entries from different SharePoint-Sites should be available to select.

What i did until now is to create this form with the DataTable:

And now im trying to populate the Field Document Description as a DropDown with Values from a Document-library which is on another SharePoint-Site.

This is the Code i have for now:

Appendix1 is the DataTable
Material is the external List-Name
Complete Document Name is the Column of the external List from which i want the values from.
Reference is the Internal Name of the Column in the DataTable Appendix1

Dear @Dario_Chiga,
You're following this instruction, correct?

One thing I definitely see is that Complete Document Name cannot be an Internal Name of a SharePoint column, it cannot contain spaces. Please, go to the list, go to List Settings, open the Column Complete Document Name and check the Internal Name in its URL, it's going to be something else:

ah okay. that was definitly an error as i see some changes happening on the form itself when i try to edit it.

Before there was just "no Data Found" when opening the DropDown Column. But now it doesn't even collapse anymore when clicking on the arron within the DropDown.

and i'm following this guide here:

Dear @Dario_Chiga,
The right guide is here - Populate column of DataTable in SharePoint form — SharePoint forms

Judging by your code, you're using it, but double check everything.

Now, for the empty dropdown - open it again, and check browser's console for errors, it should have some valuable information.