I was using HTC Backup before. Why can't I see the backup options in HTC Backup?
The backup feature of HTC Backup is no longer available in HTC phones that use Android 6.0 Marshmallow.
When you open HTC Backup, you can only restore previous backups saved by HTC Backup to your phone.
Starting from Android 6.0, use the Android
Backup Service to automatically back up your phone to Google Drive. Also use this service when restoring your backup from Google Drive to a new phone.
See the user guide or how-tos for details.