For iPhone 7 and 7 Plus: Press and hold the Power and the Volume Up buttons simultaneously and hold them for another 15 seconds at least.Here are the different ways to do a force restart of an iPhone:
When we do a force-restart (soft reset), it resets the device’s preset power cycle and gets rid of unwanted cache data. This is one of the best solutions in the book to fix all kinds of issues related to an iOS device. Now, launch WhatsApp and try to take a backup of your data again. To quickly fix the iPhone WhatsApp backup stuck issue, go to its iCloud Settings > Storage > Backup and delete the existing backups. If you have already taken a prior backup of your data on iCloud, then it can make the process stuck.
