Xiaomi
Allow Calls During Do Not Disturb auf Xiaomi
Do Not Disturb mode on Xiaomi phones does not simply mute every call. It runs a separate filter that decides which callers are still allowed to reach you while the mode is on.
If this filter is set to a narrow option, calls from anyone outside that group get silenced without a ring or vibration, even though the call still shows up as missed afterward. That is why a caller you expected to get through never made the phone ring.
To adjust who can call you during Do Not Disturb, go to Settings ➔ Sound & vibration ➔ Do not disturb ➔ Allow incoming calls ➔ Choose an option.
From there you pick one of four levels: calls from anyone, calls from contacts only, calls from starred contacts only (Favorites), or none at all. Anyone lets every call through regardless of Do Not Disturb. Contacts only restricts ringing to numbers saved in your address book. Starred contacts only narrows it further to the Favorites you have marked yourself. None silences every call no matter who is calling.
If you need calls to always ring through for specific people, mark them as Favorites first and select the starred contacts option. If you want Do Not Disturb to stay completely silent, for example during sleep hours, none is the setting to use.