Why isn't my receipt printer opening my cash drawer?

1. Navigate to the Windows Control Panel > Printers.
2. Right-click on the Citizen CT-S310 and select PRINTER PROPERTIES.  
3. On the General tab click PRINTING PREFERENCES.

   

4. Click the ADVANCED button.

   

5. Click the plus sign (+) next to Printer Functions. Also click the plus sign next to Cash Drawer #1.
6. Click the OPEN AT: option and change it to ALWAYS. Click OK.