That board is pretty common in the CNC world. The blinking light means that it is ready to run but isn’t connected to the Mach3 software properly. There is a special driver that links the board to Mach3. It must be installed and set up to make it go. I can only guess that the software either got corrupted, removed, or never installed. I believe that I have a copy that you can install if you don’t already have it somewhere on your install disk. I believe that it is named RnRmotion.dll and it is in the Mach3/Plugins directory. The LED will turn steady ON when properly connected to Mach3.
This board can be bought for under $30 on ebay and amazon, providing you can tolerate a different style connector.
Instruction manual in english here:
http://173.26.168.182/files/BSMCEO4U%20Install%20Manual%202.8.pdf
Bill