Opening your mouth and finding no sound is one of the most common dream frustrations. It is read as feeling unheard, or as something important you have not yet found the courage to say. Trying to call for help without a voice points to helplessness in a tense situation. Losing your voice while singing or speaking in public is linked to fear of judgement. Finding it again is read as confidence returning, and it can help to notice whose attention you most want.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.