Yes common problem for me, I can not get anything to work when I first start Mach until I jog an axis via MPG. Dont use normal keyboard jogging on my machines but presume that would also work. It is a USB SS issue and has been there for a long time, 3 yrs or more. The lathe was the worst for it but I then got an Ethernet SS and it is no longer an issue on the lathe. So that proves 100% that it is an issue in the USB SS plugin. As said the workaround is to jog an axis via MPG for me when I first start, usually I have to change from the axis I am currently on but so try jogging an axis and if it doesnt jog try another and then see if everything starts to work again.
Hood