When your iPhone sends incoming calls directly to voicemail or is disconnected after a ring, it might be due to various reasons. This can occur if the recipient's phone is powered off, in a low signal area, or if they have enabled the "Do Not Disturb" mode. Additionally, the contact's number may be blocked or marked as spam.

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Sudden disappearance of contacts on iPhone I just read through a thread about other people experiencing this โ€” and the solutions given, which were syncing the iCloud contacts off and on, and restoring a backup, I've already tried.