MBP refusing to boot from fileVault encrypted SSD after motherboard replacement

Changed the motherboard/logic board of a MBP 13" 2014 model. After the operation it just shows a blinking question mark when starting. I can however boot it from a High Sierra USB drive and when it logs in there it asks for the password to unlock the internal SSD, showing that it can read the SSD.

I can also mount the SSD in a MBA 13" 2013 that I have and it will boot from the SSD, like it happens with FileVault encrypted disk, it boots and the log in screen appears very quickly.

I have tried SMC reset and NVRAM reset on the MBP but no luck. I don't understand why it won't boot to the login screen with the encrypted SSD on the MPB? Is there something I can do about it?

It's kind of a work around but why not try decrypting it with the MBA, then seeing if the MBP boots it. If it does, then re-encrypt it and see if that works.