try

app.py

@@ -521,8 +521,8 @@ with gr.Blocks(theme='huggingface', css=css_buttons) as demo:
                     for voice_filename in VOICES[i:i+7]:
                         voice_filename = voice_filename[4:-4]  # drop wav/ for visibility
                         button = gr.Button(voice_filename, elem_classes=["cool-button"])
-                        button.click(fn=update_selected_voice,
-                                     inputs=[gr.Textbox(value=voice_filename, visible=False), text_input],
+                        button.click(fn=lambda: update_selected_voice(voice_filename, text_input.value),
+                                     inputs=[],
                                      outputs=[selected_voice, text_input])
                         voice_buttons.append(button)
         generate_button.click(fn=other_tts,