I had the same problem even after I installed the CH341SER driver. At last I installed FTDI official drivers from here: https://ftdichip.com/drivers/. I chose the Windows Driver Installer (VCP & D2XX) option. After I installed this, the problem in the Device Manager disappeared and my Arduino IDE was able to recognize the board in a COM port.

Hello again, I have just tried my Nybble with batteries. Both the blue and yellow LED lights have lit up and I have been able to upload a test sketch without any problem. I thought it wasn't necessary to use batteries in order to upload anything, but in my case at least it has worked this way. Thank you very much.

Ok, I'll try it. However, it will take me some time as I haven't bought them yet. I'll maintain you informed, thank you.

Hi, these are the pictures you asked for. I hope they have enough quality. From the start I realized the uploader socket adapter (shown in the next picture) was missing a pin, but I thought it was normal. Could that be the problem?

Hi, these are the pictures you asked for. I hope they have enough quality. From the start I realized the uploader socket adapter (shown in the next picture) was missing a pin, but I thought it was normal. Could that be the problem?

@Rongzhong Li My problem is that when I connect the FTDI uploader correctly (DTR pin to DTR socket) the blue LED doesn't light up. Should I suppose that if it doesn't light up the board doesn't get enough power and that's the reason the sketches I try to upload fail? Could it be a hardware problem? Is there anything more I can try?

I know the batteries I tried aren't the correct ones, but I just wanted to get any kind of response from the NyBoard. At least I got that the yellow LED lighted up. I got an email telling the kit had been shipped the 14th of January, I don't remember when it arrived. Regarding the board selection, from the start I'm selecting Arduino Uno board in the Arduino IDE for uploading sketches.

I have tried in both directions and I always get the same error when uploading a sketch. However, when I connect the uploader wrongly (matching the DTR pin in the uploader with the GND socket of the board, as shown in the following picture) the blue LED in the NyBoard lights up when uploading a sketch. When I connect the uploader correctly (matching GND pin-sockets) the blue LED doesn't light up. In relation to the batteries, firstly I have to remark they aren't the batteries recommended in the documentation for powering servos, they are normal 1.5V batteries. They are connected as shown in the following picture. When the batteries are connected the yellow LED of the NyBoard lights up, as shown in the following picture, but not the blue LED.

I already installed the drivers you mention, but my computer still wasn't recognizing the FTDI uploader. Thus, I installed other drivers from the official FTDI site (https://ftdichip.com/drivers/). After that my computer recognized the NyBoard in port COM4. When I connect the FTDI uploader its TX and RX LEDs blink for about a second in red, but the power LED doesn't switch on. If I try to upload a sketch after a time I get this error. I keep supposing the problem is the Nyboard is not getting power as its blue LED is off when I connect the FTDI uploader. Even if I connect batteries it still doesn't switch on.