diff --git a/caimira/apps/calculator/__init__.py b/caimira/apps/calculator/__init__.py
index 0c3505c2..fe1898eb 100644
--- a/caimira/apps/calculator/__init__.py
+++ b/caimira/apps/calculator/__init__.py
@@ -256,6 +256,10 @@ class ArveData(BaseRequestHandler):
         client_secret = self.settings['arve_client_secret']
         arve_api_key = self.settings['arve_api_key']
 
+        if (client_id == None or client_secret == None or arve_api_key == None):
+            # If the credentials are not defined, we skip the ARVE API connection
+            return self.send_error(401)
+            
         http_client = AsyncHTTPClient()
 
         URL = 'https://arveapi.auth.eu-central-1.amazoncognito.com/oauth2/token'
@@ -345,9 +349,9 @@ def make_app(
         # COOKIE_SECRET being undefined will result in no login information being
         # presented to the user.
         cookie_secret=os.environ.get('COOKIE_SECRET', '<undefined>'),
-        arve_client_id=os.environ.get('ARVE_CLIENT_ID', '<undefined>'),
-        arve_client_secret=os.environ.get('ARVE_CLIENT_SECRET', '<undefined>'),
-        arve_api_key=os.environ.get('ARVE_API_KEY', '<undefined>'),
+        arve_client_id=os.environ.get('ARVE_CLIENT_ID', None),
+        arve_client_secret=os.environ.get('ARVE_CLIENT_SECRET', None),
+        arve_api_key=os.environ.get('ARVE_API_KEY', None),
 
         # Process parallelism controls. There is a balance between serving a single report
         # requests quickly or serving multiple requests concurrently.
diff --git a/caimira/apps/calculator/static/js/form.js b/caimira/apps/calculator/static/js/form.js
index 6c0525fa..45656c78 100644
--- a/caimira/apps/calculator/static/js/form.js
+++ b/caimira/apps/calculator/static/js/form.js
@@ -314,8 +314,15 @@ function show_sensors_data(url) {
       success: function (result) {
         DATA_FROM_SENSORS = result;
         result.map(room => {
+          if (room['Details']['Online'] == false) return; // If the sensor is offline, it should not be added to the list.
           $("#sensors").append(`<option id=${room.RoomId} value=${room.RoomId}>Sensor ${room.RoomId}</option>`);
         });
+        if ($('#sensors > option').length == 0) {
+          $('#offline_sensors').show();
+          $('#DIVsensors_data').hide();
+          $('#arve_sensor_yes').prop('disabled', true)
+          return; // All sensors are offline
+        }
         populate_temp_hum_values(result, 0);
         if (url.searchParams.has('sensor_in_use')) {
           $("#sensors").val(url.searchParams.get('sensor_in_use'));
@@ -324,9 +331,11 @@ function show_sensors_data(url) {
           }));
         }
       },
-      error: function() {
-        alert('Authentication Error - Something went wrong during the authentication process.');
-      },
+      error: function(_, _, errorThrown) {
+        $("#arve_api_error_message").val(errorThrown).show();
+        $('#DIVsensors_data').hide();
+        $('#arve_sensor_yes').prop('disabled', true)
+      }
     });
   }
 };
diff --git a/caimira/apps/templates/cern/calculator.form.html.j2 b/caimira/apps/templates/cern/calculator.form.html.j2
index ffc67bd2..4e5ae90a 100644
--- a/caimira/apps/templates/cern/calculator.form.html.j2
+++ b/caimira/apps/templates/cern/calculator.form.html.j2
@@ -14,7 +14,9 @@
       <label for="arve_sensor_yes">Yes</label>
     </div>
   </div>
-  <div id="DIVsensors_data" style="display:none">
+  <p id="offline_sensors" class="red_text mb-2" style="display: none">All sensors are offline.</p>
+  <p id="arve_api_error_message" class="red_text mb-2" style="display:none; max-width: 85%;">Unauthorized - Something went wrong during the ARVE API authentication process.</p> 
+  <div id="DIVsensors_data" class="mb-1" style="display:none">
     <div class="form-group row mb-0">
       <div class="col-sm-4"><label class="col-form-label">Sensor:</label></div>
       <div class="col-sm-6">