use the immediate panel
Understanding the 6 Debugging Panels of UiPath in the easiest way possible! - News / Tutorials - UiPath Community Forum
We dont know the details, but when using a Variable of DataType: String() - a String Array you will not get the content, but the DataType when it is involved e.g. log Message, Write Line, using ToString()…
Also have a look at String.Join(" | ", yourOutPutVar)