How to fix error 400 when sending an email via GmailApi

Question

I'm trying to send emails without any attachments using GmailApi and get error 400 only in release build. Response message:

 {
      "error": {
        "code": 400,
        "message": "'raw' RFC822 payload message string or uploading message via /upload/* URL required",
        "errors": [
          {
            "message": "'raw' RFC822 payload message string or uploading message via /upload/* URL required",
            "domain": "global",
            "reason": "invalidArgument"
          }
        ],
        "status": "INVALID_ARGUMENT"
      }
    }

I'm trying to implement sending emails by making a request, but I also have a 400 error

I follow an example from Google, only changed authentication before sending

fun sendMessage(userId: String?,
                    emailContent: MimeMessage?): Message? {
   val service = createGmailService()
   var message: Message? = createMessageWithEmail(emailContent!!)
   
   message = service.users().messages().send(userId, message).execute()
    
   println("Message id: " + message?.id)
   println(message?.toPrettyString())
   return message
}



private fun createGmailService(): Gmail {
   val credential = createCredentials()
   return Gmail.Builder(httpTransport, jsonFactory, credential).setApplicationName("my app").build()
}
    
private fun createCredentials(): GoogleCredential {
   val account = GoogleSignIn.getLastSignedInAccount(context)
   val accessToken = GoogleAuthUtil.getToken(context, account?.account, "oauth2:profile email")

   return GoogleCredential.Builder()
           .setTransport(httpTransport)
           .setJsonFactory(jsonFactory)
           .setClientSecrets("11267771....googleusercontent.com", "-YJlT....uxEcdkc")
           .build()
           .setAccessToken(accessToken)
           .setRefreshToken("")
}