Gcode files won't print

[MaximusArael020 0]

Hi!  First time posting.  I have Cura 4.9, with a Monoprice Select Mini 3D printer V2.  Some gcodes that I have work absolutely fine and print well.  All the ones I've been trying recently do not seem to work.  I import them into Cura, hit the slice button, and export as gcode.  When I try to print them, nothing happens.  The Extruder and Platform heat up, but no movement.  What am I doing wrong?  I'm very new to this.  Thanks!

[GregValiant 1,330]

With a model loaded in Cura, and with your settings configured, select "File | Save Project" and post the resulting 3mf file here.  Post one of the "good" gcode files as well.  It may be something in the "Start-Up G-Code" that is causing the problem.