It may have to do with your SS drive. The Acronis is based on the 2009 version and not updated that often. Paragon, EaseUS and Macrium all have free versions of backup software. They are not full featured but they will make a disk image but not incremental updates. Maybe one of those will work for you.
The WD Acronis was created mainly to clone or image your drive so you could copy it to a new one. I’n not sure if it will do incremental backups either. Incremental backups is frequently a pay feature. I don’t know much about the Windows backup I use paid Acronis 2010 .