Getting a 'missing_event' response on identify API v2

Hi,

Seems like the API https://api2.amplitude.com/identify is broken. 

I tried sending a JSON payload using https://api2.amplitude.com/identify, but I keep getting a very vague error message: HTTP 400 missing_event.

I am sending the call using POST with a Conten-Type of “application/json”.

I have tried a few different JSON Payload:
 

{
    "api_key": "MY API KEY",
    "identification": [{ "user_id": "b2d0dc3e-7ec4-48ad-bdbf-30723d461067", 
 "user_properties":{"province":"ON"}}]
}

{
    "api_key": "MY API KEY",
    "identification": "[{\"user_id\":\"b2d0dc3e-7ec4-48ad-bdbf-30723d461067\", \"user_properties\":{\"$set\": {\"province\":\"ON\"}}}]"
}

I also tried

{
    "api_key": "MY API KEY",
    "identification": "[{\"user_id\":\"b2d0dc3e-7ec4-48ad-bdbf-30723d461067\", \"user_properties\":{\"province\":\"ON\"}}]"
}

I also tried using Postman. 

Each time I get a HTTP 400 missing_event.

Could the API be improved so that we get a detailed error message also.

Thank you