Since today afternoon, I am not able to open / access WhatsApp on my Lumia 520 running Windows Phone 8.1. What is the problem? How to solve it? I tried to uninstall and reinstall WhatsApp but it did not work. Can anyone help me?
The reason for a Tile to have a dark overlay is because the ChannelUri (the route that push notifications are sent) for the tile isn't working.
this has happened with Whatsapp before (in fact, it affected iOS and Android at the same time). It's something that is server-side that you have no control over, so reinstalling the app wont help.
It's truly a waiting game until WhatsApp fixes the issue.
Note: There is one other possibility, but since only one of your apps is affected I doubt it's the cause, however it's worth mentioning. When Windows Phone 8.1 is doing a backup, it will disable certain apps during the update (while it copies the data from the app's storage). To confirm if this is what's afecting you go to Phone > Settings > Backup to see if you're currently backing up.
Check this link as well
i too was facing the same problem , i wasnt able to launch whataspp , the tile was grayed out, it wasn't visible in apps section in storage sense, and also there was no view and share options even in store page
after doing a manual backup of apps and settings , i got back whatsapp without any loss of data
Settings -> Backup -> apps+settings -> back up now
hope this resolves your issue as well....!!!