Here’s a possible solution to the problem of calls going to voicemail. Somehow an iOS 17 update erroneously put in a do not disturb schedule in the Do Not Disturb area. You have to delete this erroneous do not disturb schedule.
Currently, I’m using an iPhone 11 with iOS 17.4.1. I hope this solution works for everyone.
Step 1. Go to Settings>Focus
Make sure Share Across Devices isn’t on.
Step 2. Go to Settings>Focus>Do Not Disturb
Scroll down to Set A Schedule.
Delete the schedule that’s erroneously in there.
I did this on my Mac Mini too just in case.
It solved the problem for me. I hope this solution works for everyone.