The HP6644A (and others) front panel plate, as seen on https://www.wanhunglo.com/2019/hp-6644a-refurbishment-front-panel-back-protector-p14f

If you can, please use the RSDOC (RS DesignSpark) file as that's my original source file. The STL is just an export that might not have had the perfect settings for your printer and/or application ticked or might even be incomplete.