This FAQ will help you resolve the 'TAPI Operation Failed for unknown reasons.' pop up error when starting InduSoft or the Secure Viewer.
TAPI refers to Microsoft's Telephony Application Programming Interface. It is linked to the windows Telephony service. Disabling the Telephony service will cause this error to no longer appear.
The Telephony service can be used to control dial up modems and phones. This is not something most InduSoft installations require and can be safely disabled.
To disable it, open up Services by either clicking Start, typing 'services', and clicking Services or by opening up a Run dialog and typing 'services.msc' and pressing Enter. Then browse to 'Telephony', right click it, choose 'Properties', and set 'Startup Type' to 'Manual' or 'Disabled', and OK out.
Usually the above procedure will stop this pop up from appearing. However in some rare situations, the error will still pop up. To make it stop, renaming the file called IndTapi.dll located in the InduSoft install directory\Bin folder will cause the error to no longer appear.