I recently resubscribed to IF Pro only to find that all live traffic presents itself as Unknown and doesn’t actually appear at airports. And on the map they all appear as small prop planes. Flight plans also don’t appear.
From what I know there is nothing you can really do. Check if your internet connection is okay. Sometimes also the servers have some issues or other pilots. This problem appears most likely only at busy airports or as mentioned above when IF has server issues.
From the screenshot posted, it appears that traffic is pretty sparse, and while there may be loss of information when there are plenty of planes in the vicinity of each other, this is clearly not the case.