Hello Nickz93, I do understand the inconvenience you have faced and I will be more than glad to assist you.
My suggestion for this kind of behavior is to connect the SSD to the computer where you set up the encryption and delete or disable the password. Have you tried that?
The reason why the SSD cannot be use on the new motherboard could be related to the chipset of the board.
Also make sure the SSD is connected to the SATA port 0.
Regards,