Always detect folio in box with sensor or similar

I have a box where folios come from a printer.
I need to know when there are folios in the box. What sensor do you recommend?
I have tested KY-032 and it detects the folio when it enters, but then says that there is no folio.
I need a sensor that says there is folio, and until the folio is not removed continue to say that there is folio.
Thank you very much.

We cannot help to fix code that we cannot see. Post the code per the "how to use this forum-please read" stickies. Post a schematic of the circuit, as well.

The KY-032 should work. Explain how you have the sensor arranged, or post a picture.
Post your code, using code tags.