When the original CPU failed, you took out the MMC Card and put it in the new CPU and it worked fine. Then, after cycling power on the new CPU, the program did not work.
It is possible that after the sudden shutdown in power, working memory in the CPU or the program on the MMC was not initialized correctly. Whenever I have a power loss, when the power is restored, I like to do a manual reset on the CPU. That should allow the MMC program files to be recognized correctly.
Now that power has been restored and the program loaded, do a manual reset to insure that the program image on the MMC card is good.