Push notification not working

the problem I am having is with Push notifications in Android. In order to receive my WhatsApp notifications I need to manually launch the application, which I don't want do. I want to be able to receive my notifications at any time... I've heard that it might be due to the Push Notification not working so, I decided to download from Google Play the app PNF No-Root which changed the heartbeat interval to 5 minutes (I use WLAN connection) and it didn't work at all (the same for similar apps). I tried looking for other solutions. I went to Settings > Data Usage > WLAN > WhatsApp to check if the Restrict background data box was unchecked, it was unchecked. I also went to Apps > WhatsApp to see if the box "Show Notifications" was Checked. Went to WLAN > ADVANCED and set "Keep WLAN on during sleep" as "Always". Finally, I launched WhatsApp and all the settings are correctly set for me to receive, but I don't. When I go to Apps > Running > Whatsapp it says that there is 1 Process and to Services (although it shows 1 service sometimes), ExternalMediaManager and MessageService. My device is a Lenovo A5000 with Android OS 4.4.2 I don't know what else to try, thanks.