Index: simulator/plugins/alarms/loader.py
===================================================================
diff -u -r1b402ab005844b85b8361ae611664731cfa39e0b -rd0b375c0743a71e5fb0e3211ad15cc9404e5aa5d
--- simulator/plugins/alarms/loader.py	(.../loader.py)	(revision 1b402ab005844b85b8361ae611664731cfa39e0b)
+++ simulator/plugins/alarms/loader.py	(.../loader.py)	(revision d0b375c0743a71e5fb0e3211ad15cc9404e5aa5d)
@@ -70,7 +70,7 @@
     eColMessage = 5
     eColCount = 6
 
-    eRowMute = 6
+    eRowMute = 9
 
     # column: (width, text)
     fixedLabels = {
@@ -295,11 +295,11 @@
         the slot for mute button
         :return: none
         """
-
-        if self.lstFlags.item(9).checkState() == Qt.Checked:
-            self.lstFlags.item(9).setCheckState(Qt.Checked)
+        print(self.lstFlags.item(self.eRowMute).checkState())
+        if self.lstFlags.item(self.eRowMute).checkState() == Qt.CheckState.Unchecked:
+            self.lstFlags.item(self.eRowMute).setCheckState(Qt.CheckState.Checked)
         else:
-            self.lstFlags.item(9).setCheckState(Qt.UnChecked)
+            self.lstFlags.item(self.eRowMute).setCheckState(Qt.CheckState.Unchecked)
         self.do_send()
 
     @Slot()