Media encoder PNG sequence

Hello there,

I want to stitch PNG pictures together into a MP4 file. Unfortunately when I import the first frame, ME doesn't recognize the rest of the PNG files and renders only 1 picture.

Is there a fix for that or am I doing something wrong? I'm using version 13.1.5 due to a lot of render bugs and errors in the more recent versions (14.8, 14.9, 14.7).