Push Notification API returning "invalidated": null in response

I just attempted to send a few push notifications that were not received by the devices. When I went to look at the response of the messages, this was the data that was returned:

I have X’ed out my app ID and tokens.

  {
    	"data": [{
    		"token": {
    			"id": "df15e9845ad89e82da5a01e9056690d4",
    			"type": "ios",
    			"token": "XXXXXX",
    			"created": "2017-01-25T23:08:32.485152+00:00",
    			"invalidated": null,
    			"app_id": "XXXXXX",
    			"valid": true
    		},
    		"created": "2017-01-25T23:21:28.382894+00:00",
    		"uuid": "ab48d169-16fc-4bae-aa06-2a249e916538",
    		"user_id": null,
    		"status": "queued",
    		"error": null,
    		"notification": "49b7b6ab-e665-4bfa-a89f-a54dc4b05f9d"
    	}, {
    		"token": {
    			"id": "2ef03ade29c079a5f221a84f01928fbd",
    			"type": "ios",
    			"token": "XXXXXX",
    			"created": "2017-01-25T22:27:22.152018+00:00",
    			"invalidated": null,
    			"app_id": "XXXXXX",
    			"valid": true
    		},
    		"created": "2017-01-25T23:21:28.382698+00:00",
    		"uuid": "ce8530f9-8e8f-4421-839f-6481271f8c19",
    		"user_id": null,
    		"status": "queued",
    		"error": null,
    		"notification": "49b7b6ab-e665-4bfa-a89f-a54dc4b05f9d"
    	}, {
    		"token": {
    			"id": "cfbda160bb97e65e1917ec4b5ae49f66",
    			"type": "ios",
    			"token": "XXXXXX",
    			"created": "2017-01-25T18:30:35.850015+00:00",
    			"invalidated": null,
    			"app_id": "XXXXXX",
    			"valid": true
    		},
    		"created": "2017-01-25T23:21:28.382464+00:00",
    		"uuid": "6c13cbd3-6399-4e99-93a1-ae21e2917c25",
    		"user_id": null,
    		"status": "queued",
    		"error": null,
    		"notification": "49b7b6ab-e665-4bfa-a89f-a54dc4b05f9d"
    	}, {
    		"token": {
    			"id": "76718eefb4a41e316ff1c855807f73d4",
    			"type": "ios",
    			"token": "XXXXXX",
    			"created": "2017-01-25T18:21:26.248220+00:00",
    			"invalidated": null,
    			"app_id": "XXXXXX",
    			"valid": true
    		},
    		"created": "2017-01-25T23:21:28.382262+00:00",
    		"uuid": "2d701eac-88fd-44be-b285-d63852233319",
    		"user_id": null,
    		"status": "queued",
    		"error": null,
    		"notification": "49b7b6ab-e665-4bfa-a89f-a54dc4b05f9d"
    	}, {
    		"token": {
    			"id": "4a87682514787f8f2c2a9f70962502b0",
    			"type": "ios",
    			"token": "XXXXXX",
    			"created": "2017-01-24T23:39:33.554123+00:00",
    			"invalidated": null,
    			"app_id": "XXXXXX",
    			"valid": true
    		},
    		"created": "2017-01-25T23:21:28.380017+00:00",
    		"uuid": "27bfc47e-5cbd-4288-9a1e-55221eaa7f8d",
    		"user_id": null,
    		"status": "queued",
    		"error": null,
    		"notification": "49b7b6ab-e665-4bfa-a89f-a54dc4b05f9d"
    	}, {
    		"token": {
    			"id": "4ed531db457186814b388e085c101f33",
    			"type": "ios",
    			"token": "XXXXXX",
    			"created": "2017-01-24T23:38:07.342337+00:00",
    			"invalidated": null,
    			"app_id": "XXXXXX",
    			"valid": true
    		},
    		"created": "2017-01-25T23:21:28.379815+00:00",
    		"uuid": "312e410a-4d74-4edd-969e-6be2303e00c1",
    		"user_id": null,
    		"status": "queued",
    		"error": null,
    		"notification": "49b7b6ab-e665-4bfa-a89f-a54dc4b05f9d"
    	}],
    	"meta": {
    		"status": 200,
    		"request_id": "146ce355-a9f5-4545-c585-b2a4cc0e4830",
    		"version": "2.0.0-beta.0"
    	}
    }

I couldn’t find any information on that invalidated tag in the response. Any thoughts or clues to help with this issue?