Hello GerryR,

Please check your MS509 is a fake or not (See post below and check serial number)
http://pro.auteltech.com/autelsupport/Diagnostic%20System/339.jhtml?createrId=45&view=1

If you have a real product, do you have the USB to Serial software/driver installed ?
Check your device mananger to see if you get the yellow "?" if the scanner is connected.

An other issue is, that the Autel software uses the highest serial port configured on the PC to talk to the MS509. If you have installed an other device that uses this "usb to serial" technology after the Autel driver (GPS tracker...) you might have a new serial port and the software tries to use this and not the original for the MS509.

Ensure that the highest serial internface (COMx) is the one the MS509 uses when connected to the PC. Then it should work fine.