Q: Unable to download/update apps in wifi only

Hello Immankan,

Thanks for using Apple Support Communities.

From your post I understand that you're unable to update apps on your Wi-Fi connection on multiple iOS devices.  To start troubleshooting this issue on both devices, please sign out of your account, restart the devices, and then sign back in to your Apple ID.

iTunes, iBooks, and App Store

1. Tap Settings > iTunes & App Store.
2. Tap your Apple ID. If you see the option to Sign In, you can change your Apple ID now.
   
3. Tap Sign Out.
4. Go to Settings > iTunes & App Store.
5. Enter your Apple ID and password, then tap Sign In.
   

Sign in with a different Apple ID on your iPhone, iPad, or iPod touch - Apple Support

How to restart

1. Press and hold the Sleep/Wake button until the red slider appears.
2. Drag the slider to turn your device completely off.
3. After the device turns off, press and hold the Sleep/Wake button again until you see the Apple logo.

Restart your iPhone, iPad, or iPod touch - Apple Support

Take care,

Alex H.