MGE UPS USB connection problem

[N1K]

I'm having problems with my MGE UPS 300VA with serial/usb connection...

Let's start from the beggining when I bought it..

I connected USB to my PC with USB cable and load windows, windows detected it and everything was working fine. I could see the state of the battery, the manufacturer information etc.

Then one day when I powered my computer it stopped on P4C800 Deluxe MB screen and stayed that way until I disconnect USB cable from UPS...

When windows loads I reconnected UPS and the message says:

USB device not recognized or is malfuctioning..

Off course I called service for it and then service technician changed the "card" in it.. (probably USB/serial connection card )

Then it worked for some time and then again the same error, and this time service techinician told that on his computer UPS is working normally..

I brought it home and connected it and UPS was working normally???????

It worked for a month and now again the same problem....

I connected it with serial cable and then tried to install MGE app which detects this UPS through serial connection and error states that UPS cannot be detected..

It seems that this card that was changed by technician again is working problems...

What should I do??