Skype For Business - Receive IM not working with the below steps

Question

I am developing a skype java rest based app for "skype for business". I am able to send im, authorize etc. But, I'm not able to receive IM. The events object take too much time to respond for my postman request. And, there are no incoming IM shown in my events object.

But the receive Message IM feature is not working.

The steps I have followed are

1) generate access token and access my ucwa application. 2) make user online with makeMeAvailable api. 3) get request for ucwa application generated. 4) and call the events href link in the step 3. 5) and call the events href link in the step 4 but its giving sender array empty and no incoming or messageInvitation link.

Other Info: I am not getting any sender array or its empty. And i am periodically calling reportMyActivity api to keep user online.

Reference Document https://docs.microsoft.com/en-us/skype-sdk/ucwa/receiveanim.

I have followed the official documentaion of ucwa skype but not able to move forward.

Other Info: I am not getting any sender array or its empty. And i am periodically calling reportMyActivity api to keep user online.

Event link object :

https://webpoolpnqin102.infra.lync.com/ucwa/oauth/v1/applications/101667312687/events?ack=2&key=c2lwOm5hcmVuZGVyLmtAaW1pbW9iaWxlbW9iaS5vbm1pY3Jvc29mdC5jb20%3D-101667312687-ZGVmYXVsdA%3D%3D

Please help me.

events object I am getting

            {
                "_links": {
                    "self": {
                        "href": "/ucwa/oauth/v1/applications/101667312687/events?ack=2&key=c2lwOm5hcmVuZGVyLmtAaW1pbW9iaWxlbW9iaS5vbm1pY3Jvc29mdC5jb20%3D-101667312687-ZGVmYXVsdA%3D%3D"
                    },
                    "next": {
                        "href": "/ucwa/oauth/v1/applications/101667312687/events?ack=3&key=c2lwOm5hcmVuZGVyLmtAaW1pbW9iaWxlbW9iaS5vbm1pY3Jvc29mdC5jb20%3D-101667312687-ZGVmYXVsdA%3D%3D"
                    }
                },
                "sender": [
                    {
                        "rel": "me",
                        "href": "/ucwa/oauth/v1/applications/101667312687/me",
                        "events": [
                            {
                                "link": {
                                    "rel": "presence",
                                    "href": "/ucwa/oauth/v1/applications/101667312687/me/presence"
                                },
                                "type": "updated"
                            }
                        ]
                    }
                ]
            }