If some repair on ESC or motor was done a complete Motor-assignment is absolutely needed. But for this you need the GUI working.
First step is to check if driver are correct installed. If you plug in the white cord (this is a simple serial to USB converter by the way) to th PCs USB in Windows Device Manager should appear a new device for COM&LPT.
A virtual COM port should be assigned to this device, a COM number (here COM3). If so, all is OK. The GUI should recognize this COM port by itself but can also force it to connect to it.
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The problem may then be the tiny connector inside the battery compartment. Please check if no pin is bent (4 pin in total) and wires are OK.