My app will not build! Something keeps going wrong when it trys to build my app

Hi, I’m very new to this but my app is basically only a web viewer of a google site (new google sites) and works when I perform a live test on my phone using the thunkable app but when I click download so that thunkable can build my app I get emails saying the app won’t build because there is something wrong with it. It says a command failed and that there was an unexpected EOF while looking for matching `’’ /bin/sh: -c: line 1: syntax error: unexpected end of file. What does this mean? Is there a fix for this?