NASLite Network Attached Storage

I have been running naslite for many years now and have just had a motherboard failure. I have replaced the board with Gigabyte GA-F2A88x-D3HP the old board was a GA-F2A88X-D3H.
I am having a problem with the unlock code. When first started I generated a new ID code and a restart after inputing that and saving config gave me what appeared to be a clean bill of health.
I had to switch off to finalise work on cable tidying etc and I left it off for 48 hours. At the next restart the unlock ID showed as invalid so I generated the unlock ID again entered it saved and did a restart. All ok again.
I had to shut down again and the same thing happens again and I am getting the same 2 codes being generated now. One will work until the next reboot then I generate again and get the second one repeated.
I am at a total loss as to why this is happening. Can any one offer a solution.