Most likely you are accessing e.Vtq but e.Vtq is null. You need to do appropriate error checks: Test whether e.Exception is null first. If it is, only then you can access e.Vtq. If e.Exception is not null, you need to deal with the error that is described in the e.Exception.

See opclabs.doc-that.com/files/onlinedocs/QuickOpc/Latest/User%2...%20the%20actual%20result_.html , and also our examples, for proper error handling code.

Then, of course, the question is, what was it that caused e.Vtq be null? If you write some proper error handling and display or log e.Exception somehow, you would know what the error was, and that would give you the chance to address it.

You are right that licensing problem is actually a likely cause. If so, you need to install the license on the runtime computer, or embed it into your application. You do not need to uninstall it from the development computer. See opclabs.doc-that.com/files/onlinedocs/QuickOpc/Latest/User%2.../webframe.html#Licensing3.html .

Even if the missing license key was actually the cause of your problem, and installing it resolves the issue, you should fix the error handling code, because there are all other kinds of errors that can occur, and you r application needs to deal with that.

Best regards