The code for creating user with AdditionalData does not seem to be correct

[MhAllan]

I have tried This Code to create users with custom data. Evenything was working fine with AD Graph Client, but with MS Graph Client (All new app was created and permissions were set according to all docs) .. but I keep getting this error when I call AddAsync:

Message: One or more properties contains invalid values.
Inner error:
	AdditionalData:
	date: 2021-06-22T14:24:45
      . . . 

When I use wrong attribute name or wrong extention app id I get this error

Code: Request_BadRequest
Message: The following extension properties are not available: extension_XXXX...XXX_MyProp.
Inner error:
	AdditionalData:
	date: 2021-06-22T15:11:44

[MhAllan]

Apparently the issue is about missing identity but the error is not clear at all and writes AdditionalData: which made me think the problem is in AdditionalData!

[LockTar]

AdditionalData just means "here is some extra information that could be related to your issue"...