You could offer a reminder, with a calendar entry to make it easy for them.

I'd offer a bonus to keep them engaged, such as a cheat sheet or a compelling case study. For example, tell a story of a patient who went from before to after, and spell out the patient's experience from "My knees were so bad, I couldn't get out of bed" to "I won the Olympic 100 metre sprint". If it's a short video, even better.

Doctors, from my experience, are not impressed by more statistics, or at least not engaged by them. But how this SaaS experience meant that Mrs Johnson never missed her appointment (because it sent her a reminder), or how Mr Smith didn't have to wait around for that old clunky patient CRM system that was keeping the waiting room crowded out, can be more attractive to the doctor.

In other words, you're not selling the solution for the doctor or the clinic; you're demonstrating the improved experience for the patient. Tell the patient's story, and the doctor is more likely to accept that calendar invite for the demo.