iOS 11 has been reported with many troubles out of which one is related to clock on lock screen. After upgrading the iphone to iOS 11 the clock from lock screen just disappeared. Even if you try to reboot your phone, it may appear after that but after sometime it would disappear again. You may try to Hard reset your iphone by: Hold down the Home and Power buttons at the same time and continue holding them down until the Apple appears.
It is not only that your clock is missing from the lock screen but also it may cause other issues like none of notifications are coming through. iphone lights up like a notification has been received but my lock screen is blank except for my wallpaper.
There is no information visible on lock screen except status bar. Phone is still working but nothing is visible except the wallpaper. I'm able to swipe to both sided and launch camera/take picture for example but all I see is wallpaper.
How to fix the clock disappeared issue on lock screen in your iphone:
Actually its more like a workaround, When clock disappeared, just swiped top down on lock screen and the clock reappeared.
Solution 2: Other possible workaround is to change the fonts to bold and then back to normal the problem should disappears. Please check now.
Solution 3: Turn off live photos
The issue is reported majorly from the devices where 'live' photo is set as background. Please try to turn off this feature and check again the same issue with a blank lock screen. The issue should not appear after this.
If still not working Try to reset your iphone
You can use either iCloud or iTunes to back up your iOS device. For iCloud go to Settings > iCloud > Backup and ensure that the feature is enabled. To see when the last backup was run look under the Back Up Now option where the date and time should be displayed. If you haven't done a backup before you can tap the Back Up Now button and follow the instructions
What about Permanent fix:
While we contacted Apple regarding the lock screen issue iphone and they said that they are aware of the bug and the only solution right now until the next update fixes the situation is to revert to iOS 10.3.3