Sony Xperia XZ1 Manual page 30

3. Scroll down and tap Advanced options.
4. Scroll down and, under IP settings, select Static.
5. Scroll down and enter the required settings.
6. Tap Save.

Change the Wi-Fi network security of your router to a different security encryption.
For instructions on how to change the network security, check the user guide of the
router or contact your router manufacturer.

Make sure that potentially interfering devices or appliances are not placed close to the
Wi-Fi router.
Cordless phones, microwave ovens, baby monitors, wireless speakers, monitors and
video transmitters that operate in the 2.4 GHz or 5 GHz bandwidth may interfere with a
Wi-Fi network. If the problem persists, try changing the router frequency band settings
to 5 GHz or 2.4 GHz.
For instructions on how to change router channel settings, check the user guide of the
router or contact your router manufacturer.

Perform a factory data reset. This is sometimes the best solution if your device stops
functioning properly, but note that it will delete all personal content saved on the
internal memory of your device. Make sure to back up data that you want to keep.
To back up your data using a computer
Multimedia messaging isn't working
Xperia™ XZ1 Dual SIM support overview

Check that MMS (Multimedia Messaging Service) is supported by your network operator
and/or subscription.

Download settings for internet and MMS automatically.
To download internet and MMS settings
1. Find and tap Settings > Network & Internet > Internet settings.
2. Tap ACCEPT. Once the settings have been downloaded successfully,
appears in the status bar and mobile data traffic is turned on automatically.