One equipment can have two states: Enabled or Disabled. To activate an equipment, go through the following steps: 

Step 1: In the main menu, on the left side, click Locations and Equipment. 

Step 2: Choose the Locations option.

Step 3: Find the Sensor using the Free Search or select Disabled from the sensor filter and click Filter.  

Step 4: Select the desired sensor. The sensor view will open.

Step 5: Select the General tab.

Step 6: At the bottom of the page, click on Activate option.

Example of the procedure: