Can I back up my phone
Why can’t I back up my phone
Why can’t I back up my phone
Verify that you are doing these steps: How to back up your iPhone, iPad, and iPod touch - Apple Support
Verify that you are doing these steps: How to back up your iPhone, iPad, and iPod touch - Apple Support
In addition to what Siabh stated above, see - If you can't back up to iCloud or restore from iCloud backup failed - Apple Support.
Can I back up my phone