@dan Oh I see. The error in the response says:
"because it was missing a unique id in the [user.id] or enough information to store in FusionAuth (i.e. an email or username)"
In other words, "either Id or email" is missing from your request. Which makes boolean sense when thinking about it carefully.
But when first reading it, I though it meant "you need either Id or email", which is very different. I supplied one of those. I though that was what the "or" meant.
This error could be better as:
"because it was missing a unique id in the [user.id] or enough information to store in FusionAuth (i.e. an email or username). Both are necessary"