AAE 6001 error code.need help.

pro tools 11.2.1 loads up, but will not play when pressing play on transport.when I press setup,then playback engine error message AAE 6001 encountered.do not know what is causing this.I am using the focusrite scarlett2i4 as my interface.any help would be great.thanks. My setup is.- Toshiba Satellite AMD-A6 Quad Core, Windows 8-64, 8GB RAM,Seagate Barracuda External Drive 7200,2TerraByte,Focusrite Scarlett 2i4 interface,