Error: "Unable to JIT the user"

Questions
1

After logging in to Google we see an error response from Okta:

?state=2pd2EE4Q0mwWjVN2wWA3ZS7eWZsQqspuI42zmG&error=jit_failure&error_description=Unable+to+JIT+the+user.

Investigating the Okta log we see:

ErrorMessagewith the following validation errors: identityid field failed validation with value ‘null’: Value for required property {0} is missing.

Could you assist us here please?

2

we have created a mapping from email to that field now – but why is it required suddenly? we still have old users with an empty field – yet new ones must be given a value for identityid. Why?

PS we are on oktapreview.com