The output from the App is just the column [Sheet Names] with the value being "Report"? Or there are other columns, but only the column [Sheet Names] is filled out? Are you able to post a screenshot of the output you are getting?
You will need to ensure that the Gallery App has the correct permissions to access the directory, this includes the app running as a user that has that access. Seeing the output log for the workflow may help as well.
@fathrizakusuma it is very hard to troubleshoot with just screenshots, but here is a macro I built on the gallery that I believe does what you are looking for. It takes a folder location and gets all the excel files and sheets out into 1 data stream.
Bacon
Without the log of what's happening in the workflow run, I'm not sure where the data is dropping off. It looks like you have enough to generate the column names, so I'm guessing it's hitting some data, but if you are not getting the filled out table, then it's obviously not right somewhere. Take a look at the output log, to see how many batches ran on the macro and how many records went through.