Try turning off notifications, reboot and turn it back on. Try cache wipe from android recovery. Try going into notifications settings and double check apps are enabled. If all else fails, backup all important data and do a factory reset through android recovery.
Hey @DoggyTrouble, we are sorry to hear about your experience with missing feature after Oreo update. I will make sure to forward to development team and hope to see the change in the future release! Thanks for your feedback!