Critical Alerts

I reset my iphone. I have version 15.6.1 on my iphone 11. After resetting the phone, I no longer am able to Allow Critical Alerts to any app. The option does not appear anywhere. I am useing Critical Alerts with my Dexcom G6 glucose monitoring system and not having them makes the Dexcom G5 app non-functional. Please let me know if you have any solutions to this issue.