Thank you for responding. Here are the screenshots that may be of use to finding the solution.
Context:
1. Screenshot_178 is my screen before I enter the path of my TxtInOut
2. Screenshot_179 is my screen after I enter the path of my TxtInOut (** I run the app through the browser because the popup app suddenly close and needs the R session to be restarted before it shows up again, the pic here became somewhat filled with white but not processing forward)
3. Screenshot_180 shows the warning error that I think caused the closing of the app in my case.