When was it purchased? Do you still have warranty for it?
If your warranty is expired, or you want to diagnose it by yourself, power off the Nucleus+, disassemble it and remove the m.2 boot SSD. Power it on and see if anything shows on the monitor.
Ben with the support team here, thanks for writing in! I wanted to check in on this thread to see what your status is. Are you still having issues with your Nucleus?
@wklie is correct in that your symptoms do sound like potential SSD failure.