No Dial Tone for Incoming Callers

I am experiencing an issue where incoming callers receive no dial tone when calling my personal desk phone. For example, I will call my desk phone from my cell phone and receive no dial tone or ringing on the cell phone. This is happening when calling from other internal phones as well. This is a desk phone not a call queue so the “Audio while connecting” setting does not apply. I've resynced the desk phone, power cycled the phone, inspected call rules, even swapped the phone entirely. All without resolution. Any help would be appreciated.