/users/v1/users/ returning "Validation failed" error

I've been hitting this endpoint to create new users since Feb 2024. As of yesterday, this route has begun returning a “Validation failed” error for all my requests, even when I send known-unique data and verify that the API key I'm using works for other routes.

Here's what the response now looks like:

{
  "error": "Validation failed",
  "details": null,
  "path": "/users/v1/users",
  "request_id": "..."
}

Troubleshooting I've done so far:

Step	Result
Confirmed our API key is valid and works on other endpoints	✅
Generated a new API key and re-tested	✅ Still fails
Tried multiple brand-new users with unique phone and email addresses	✅ Still fails
Executed the request via both our application and your API Explorer	✅ Same failure
Checked active user count	✅ 1,232 active users out of 1,250 seats
Reviewed changelog and API docs	✅ No relevant changes found
Confirmed no new required custom fields were added	✅

Sample Request

curl --request POST \
     --url 'https://api.connecteam.com/users/v1/users?sendActivation=false' \
     --header 'X-API-KEY: XXXX(I have tried multiple keys)XXXXX' \
     --header 'accept: application/json' \
     --header 'content-type: application/json' \
     --data '
[
  {
    "userType": "user",
    "isArchived": false,
    "firstName": "testing",
    "lastName": "testpleasedelete",
    "phoneNumber": "+14809651666",
    "email": "[email protected]"
  }
]
'

Recent Request IDs

Here are some of the recent failed attempts for reference:

69f090ed-f17a-474d-b844-4ef0329362f8  
de0824f4-5efb-4fea-88bb-c47138dc8eca  
8e161ad7-9d67-49c7-bc1c-0fb716cedcd7  
6e876c81-adad-49dd-a4ca-00a4ac49ea28  
5a7355ee-1e80-4f46-8841-77756858d173

Could you please help us identify which validation rule is failing? If something changed recently (e.g., schema requirements, custom field rules, or seat limits), any clarity or workaround would be greatly appreciated—we rely on this route heavily.

Thanks!