@KyleStachewicz
There is no built-in function within Canvas to notify students when they're not accessing Canvas. However, there are multiple ways to achieve this.
Manually
There is a built-in admin report with a list of students and their last access to Canvas, you can pull this report by going to Admin page -> Settings -> Reports -> Last User Access. Then use this list to send out emails manually.

Automatically 🚀
If you have access to Canvas Data 2 you can create a more sophisticated report. You might need to contact your CSM to enable Canvas Data 2 for your institution.
Combining data from Canvas Data 2 with a workflow automation tool, you can automate this whole process. You can check out how to set it up the tool here: https://community.canvaslms.com/t5/Canvas-Developers-Group/Automate-Canvas-with-n8n/ba-p/585337
I'll attach a workflow to automate this process here in the next few days.
Please feel free to PM me if you need help setting this up.