[READ] Step 1: Are you in the right place?

yes

[REQUIRED] Step 2: Describe your environment

• Xcode version: 10.2
• Firebase SDK version: 5.20.2
• Firebase Component: InAppMessaging + InAppMessagingDisplay
• Component version: 0.13.0 + 0.13.1

[REQUIRED] Step 3: Describe the problem

Reopening #2816 - I cannot receive test messages on device or simulator.

Steps to reproduce:

Add the following to your Podfile:

  pod 'Firebase'
  pod 'Firebase/InAppMessagingDisplay'
  pod 'Firebase/Analytics'

• Run pod install
• Build and run the app in the simulator or on a device.
• Open Firebase Console and create a new In-App Messaging campaign with style: Modal.
• Under options select Test on Device, add your InstanceID, and click Test.
• Background the running app, then open it again.

The following error is logged to the Xcode console:

2019-09-19 15:17:02.421473+0200 My App[6754:458265] 5.20.0 - [Firebase/InAppMessaging][I-IAM130004] Failed restful api request to fetch in-app messages: seeing http status code as 400 with body as {
  "error": {
    "code": 400,
    "message": "Request contains an invalid argument.",
    "status": "INVALID_ARGUMENT"
  }
}

Relevant Code:

None