diff --git a/src/main.cpp b/src/main.cpp
index 4503c12..0fe2d2b 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -42,10 +42,24 @@ void midi_task(void* parameter) {
             mux.show();
         }
 
+        // If no clock ever arrives, flash pixel 6 red periodically so user knows
+        static uint32_t last_noclk_flash = 0;
+        if (tick == 0 && now - last_noclk_flash > 3000) {
+            last_noclk_flash = now;
+            mux.set_led_color(6, 255, 0, 0);
+            mux.show();
+            delay(150);
+            mux.set_led_color(6, 20, 20, 20);
+            mux.show();
+            Serial.println("[CLK] !! NO MIDI CLOCK RECEIVED - check Loopy Pro sync settings !!");
+        }
+
         static uint32_t last_diag = 0;
         if (now - last_diag > 2000) {
             last_diag = now;
-            Serial.printf("[CLK] ticks=%lu beat=%lu\n", (unsigned long)tick, (unsigned long)last_beat);
+            Serial.printf("[CLK] ticks=%lu beat=%lu mounted=%s\n",
+                          (unsigned long)tick, (unsigned long)last_beat,
+                          TinyUSBDevice.mounted() ? "YES" : "NO");
         }
 
         if (flash_start > 0) {