Default [Q] Can't download from Play Store via WiFi

Hello guys. This is my first post on the forum. My problem is that my phone running 4.2.1 can't install apps or any updates from Play Store via WiFi. I haven't tested downloading with 3G yet. When I click the "Install" or "Update" button in Play Store, the d/l bar pops up with the "Waiting on network" above. the d/l never starts. I think it is because of my phone and not the WiFi router because my old LG L3 running stock 2.3.6 has no problems. My phone is currently on the stock ROM and rooted but i've flashed custom ROMs before. I've tried many solutions on the Internet like deleting Play Store's updates, data and cache, but none works. I don't want to factory reset my phone. Can anyone fix this? Thanks in advance. And sorry for my bad English if there are any mistakes.