Our SupportPlus team regularly answers this question:
Q: I just updated to a newer version of VTScada and now my modems no longer work!
A: Customers using the modem dialer feature of the Alarm Notification System must ensure that they apply Windows updates on a regular basis. Updates to VTScada will often include modem drivers that have been patched to work with the latest Microsoft updates for your version of the Windows operating system. They may not work if you have not applied those updates to your system.