Well, the gadget is likely where the issue is in this case.
Without knowing all the differences with the reference x86 gadget it will be hard to give you any advice I think. Using an efi executable signed with the incorrect keys can lead to that error, but I’m sure there are many other reasons. It’s probably a good idea to examine all the differences between the reference gadget and your own.
It appears, for some reason the key to unlock your data volume was not retrieved from the TPM. Perhaps there are more log lines before that error that can help.
This could provide some inspiration, where I had a similar error, but as I already said the reasons could be many, and could therefor be different: Changes in shim-signed packaging and breakages in UC20 secured grade model images on amd64
Cheers, Just