Does NSH wait for an interrupt from the UART to read data? If so, maybe the SAMA5D27 isn't interrupting. I tried to enable PIOD interrupts, since UART2 is on PIOD, but got some compilation errors. I'll look at it more tomorrow.
Yes, if you don't have RX interrupts, nothing will be read. If you don't have interrupts there is probably an error in either the pin configuration or IRQ number used.
