If you are trying to use the IOS mobile app outside of your home network (via 3G, LTE, ...), you must do the following:
1) Do you have ports 5150 and 5160 forwarded on your router? Are you using your Cable Modem IP address (or a DDNS) instead of the local IP address assigned by your router to the PC hosting your Dviewcam server software? Dlink provides a free DDNS service. I would recommend you use a DDNS (your ISP may change your Cable Modem IP address, the DDNS will deal with this).
2) Do you have the Remote LiveViewer and Playback servers running in your Dviewcam server software?
Even if you do get the IOS App working, you will find that it is not very good for viewing recordings saved on your Dviewcam server. You are forced to select a date/time to search for recordings and an interval from that time to search across. For some unexplained reason, the max interval you can search is 10 minutes!! So for example if you say to search from 3PM with an interval of 10 mins, it only looks for recordings made from 3:00 to 3:10, and if there are none you get a "no recordings found" dialog. How poor is that?? So other than watching a live stream with sound (you must enable the souond in dview cam settings), the IOS app is nearly useless.
I've used the IOS apps from Vivotek and Samsung, and they both allow you to search from one date/time to another and then it plays all recordings save on the server for that time interval. Not sure where Dlink came up with the lame guess your best 10 minute search interval, but that needs to be changed.