The custom charge and the shipping cost for many EU countries are expensive.
I am also not so sure since one is working out of two boards.
I commonly saw was the contact failure of DC jack which has 4.00mm diameter with 1.7mm center pin which has smaller diameter than the specified 4.75mm diameter with 1.7mm center pin assuming both DragonBoard 410C are OK.
If you have the USB-UART adapter, then it is able to retrieve more information from the serial console screen.
You may have to contact the distributor of the board, if anything does not work.